Word Ladder Puzzles: Lewis Carroll's Doublets and How to Solve Them

A word ladder is a puzzle where you turn one word into another by changing one letter at a time, and every step along the way has to be a real word. To get from CAT to DOG, for example, you might go CAT, COT, COG, DOG. The words stay the same length, the letters stay in their places, and the goal is usually to reach the target in as few steps as possible. Lewis Carroll, the author of Alice's Adventures in Wonderland, published the puzzle in 1879 under the name "Doublets," and it's been a favorite of word lovers ever since.

This guide covers the rules, the history, a reliable method for solving any word ladder, and the simple math that tells you when a ladder can't be any shorter. Every ladder on this page was checked with a short computer program to make sure each step changes exactly one letter, in place. All the words are ordinary English words you'd find in a standard dictionary.

What is a word ladder?

Picture a ladder standing on the floor. The bottom rung is your starting word, the top rung is your target word, and every rung in between is a word that differs from the rung below it by exactly one letter. Climbing the ladder means changing one letter, checking that you've made a real word, and repeating until you arrive.

Here's Carroll's own most famous example, turning HEAD into TAIL:

1. HEAD
2. HEAL (change D to L)
3. TEAL (change H to T)
4. TELL (change A to L)
5. TALL (change E to A)
6. TAIL (change L to I)

That's five changes. The chain appears in Carroll's 1879 booklet, Doublets, a Word-Puzzle, which has been digitized from a copy held at Oxford University, and it's quoted in Belle Moses's 1910 biography Lewis Carroll in Wonderland and at Home.

The puzzle goes by many names. Carroll called it Doublets. You'll also see word ladder, word chain, word links, laddergram, word golf and change-a-letter. They all mean the same basic game. If you enjoy short, satisfying word puzzles like the ones in our word jumble maker guide, word ladders are a natural next step.

The rules of a word ladder

Carroll's rules were short. As Moses quotes them, each word in the chain must differ from the next "in one letter only," and the letters "must not be interchanged among themselves." In other words, you can't shuffle letters around. Each letter keeps its own position.

Carroll also gave the parts of the puzzle names. The two given words together are the "Doublet." The words you add in between are "Links." The whole series is the "Chain." He even asked that links be words "such as might be used in good society," which is a polite Victorian way of saying "keep it clean."

Here's what's allowed and what isn't in the standard game:

Move	Allowed?	Example
Change one letter, same position	Yes	COLD to CORD
Change two letters at once	No	COLD to CARD in one step
Swap the order of letters	No	DOG to GOD
Add or remove a letter	No (yes in some variants)	BROW to BROWN
Proper nouns (names, places)	Usually no	BOB, PARIS
Abbreviations	No	ETC, USA
Plurals and verb forms	Usually yes	CATS, RAN
Rare or old-fashioned words	Depends on the dictionary you agree on	BOOR, GOAD
Using the same word twice	Pointless, since it only adds steps	CAT, COT, CAT

Before you play with friends, agree on one thing: what counts as a word. Some groups allow any word in a standard dictionary. Others stick to "words a ten-year-old would know." Settling that up front avoids a lot of arguments about whether GROAT (an old English coin) is fair.

How a ladder is scored

When there's a score, it's usually the number of steps or links. Fewer is better. The CAT to DOG ladder above has three steps (CAT to COT, COT to COG, COG to DOG) and two links (COT and COG). Most modern puzzles count steps, so that's what we'll use on this page. When a puzzle prints blank rungs, the number of blanks tells you exactly how many links the setter used.

Lewis Carroll and the invention of Doublets

Lewis Carroll was the pen name of Charles Lutwidge Dodgson, an Oxford mathematics lecturer born on January 27, 1832, according to the 1899 biography The Life and Letters of Lewis Carroll by his nephew, Stuart Dodgson Collingwood. Dodgson loved games, logic problems and puzzles of every kind, and he invented many of them.

Doublets was one of his most successful. He launched it as a puzzle series in the magazine Vanity Fair, introducing it as "a new puzzle." In 1879 the rules and puzzles were collected into the booklet Doublets, a Word-Puzzle, where Carroll described it as "a new kind of Puzzle."

He kept tinkering with the idea. In a diary entry dated December 12, 1879, quoted in Collingwood's biography, Carroll wrote that he had "invented a new way of working one word into another," and that he was thinking of calling the new puzzle "Syzygies." That later game linked words through shared groups of letters instead of single-letter changes. It never caught on like Doublets did, probably because the simple one-letter rule is so easy to explain.

When	What happened	Source
January 27, 1832	Charles Lutwidge Dodgson (Lewis Carroll) is born at Daresbury, England	Collingwood (1899)
1879	The booklet Doublets, a Word-Puzzle is published; the game had first appeared in Vanity Fair	Digitized 1879 booklet; Moses (1910)
December 12, 1879	Carroll's diary records a new word-linking puzzle he plans to call "Syzygies"	Collingwood (1899)
1910	Belle Moses's biography reprints Carroll's rules and the HEAD to TAIL chain	Moses (1910)
2012	Jon McLoone of Wolfram Research uses computer word lists to search for the longest possible shortest ladders	Wolfram blog (2012)

One small warning if you read the Moses biography yourself: the online text dates the Vanity Fair article to 1897. That can't be right, since the booklet collecting the puzzles is dated 1879. It looks like two digits got swapped somewhere along the way.

How to solve a word ladder, step by step

You can solve a lot of word ladders by poking around until something works. But a little method makes the hard ones much easier. Here's the approach that works best.

Step 1: Compare the two words letter by letter

Write the start word above the target word and mark which positions are different. For COLD and WARM, every position is different: C/W, O/A, L/R, D/M. That means you need at least four changes, one for each position. This count is your target to beat (more on why in a later section).

Step 2: Look for letters that already match

Any letter that's already correct is a gift. Try to keep it locked in place the whole way. For LEAD to GOLD, the D at the end already matches, so you only have to deal with the first three letters.

Step 3: Change the "easy" positions first

Some letter positions have lots of options. The first letter of a short word is usually the most flexible: think of all the words that end in -AT (BAT, CAT, FAT, HAT, MAT, PAT, RAT, SAT, VAT). Changing a flexible position early gives you more choices later.

Step 4: Use vowels as pivots

Vowels are the hinge of most short words. Changing a vowel keeps the consonant "frame" of the word the same, which often opens a new family of words. CAT becomes COT or CUT. BIG becomes BAG, BEG, BOG or BUG. When you're stuck, try every vowel in the middle position before giving up.

Step 5: Work backward from the target

If the front end isn't going anywhere, start from the target word and build down. List every real word that's one letter away from the target. Then check whether any of them is easier to reach from the start. Meeting in the middle is a classic trick, and it's exactly what good computer programs do too.

Step 6: Write down dead ends

Keep a little list of words you've tried that went nowhere. It stops you from walking in circles, which is easy to do with a three- or four-letter ladder.

Step 7: Shorten it

Once you have any solution, look for shortcuts. Can you skip a rung by changing a different letter earlier? Count your steps and compare them to the number of differing positions you found in Step 1. If they match, you're done: no shorter ladder can exist.

Worked word ladder examples, solved step by step

Let's apply the method to a few real ladders.

Example 1: COLD to WARM (4 steps)

All four positions differ, so the minimum is 4. Let's see if we can hit it.

• COLD to CORD. We changed the third letter, L to R. R is already the correct third letter of WARM, so that's progress.
• CORD to CARD. Second letter, O to A. Now positions 2 and 3 match WARM.
• CARD to WARD. First letter, C to W. Three letters right.
• WARD to WARM. Last letter, D to M. Done.

Four steps, which equals the minimum. This ladder is as short as possible. Notice that every single step fixed one position for good. That's what a perfect ladder looks like.

Example 2: HEAD to TAIL (Carroll's 5 steps)

HEAD and TAIL differ in all four positions, so the minimum possible is 4. Carroll's chain uses 5. Why the extra step?

Look at the third letter. It starts as A (HEAD), becomes L (TELL), and finally becomes I (TAIL). It changes twice. Meanwhile the second letter goes from E to A. Carroll needed a temporary letter in the third position to keep every rung a real word. A detour like that costs one extra step. Whether a 4-step HEAD to TAIL exists depends on which words you allow; with everyday words, it's hard to find one, which is part of why Carroll's version is still the one people quote.

Example 3: FOUR to FIVE (7 steps)

Only three positions differ here (O/I, U/V, R/E), so the minimum is 3. But try it and you'll see why that's tough. The words between FOUR and FIVE in a 3-step ladder would have to be things like FOUE, FIUR or FOVR, and none of those are words. You need to wander a bit:

1. FOUR to FOUL (R to L)
2. FOUL to FOOL (U to O)
3. FOOL to FOOT (L to T)
4. FOOT to FORT (O to R)
5. FORT to FORE (T to E)
6. FORE to FIRE (O to I)
7. FIRE to FIVE (R to V)

That's 7 steps, more than double the minimum. It's a great reminder that the lower bound is a floor, not a promise. Some word pairs are simply far apart in the "map" of real words.

Example 4: LEAD to GOLD (3 steps)

Here's one for the alchemists. Three positions differ (L/G, E/O, A/L), so 3 is the minimum.

• LEAD to LOAD (E to O)
• LOAD to GOAD (L to G)
• GOAD to GOLD (A to L)

Three steps, the minimum. GOAD (to urge or provoke) is the key word. Most people don't think of it right away, which is what makes this a satisfying puzzle.

Example 5: BLACK to WHITE (8 steps)

Five-letter ladders are a big jump in difficulty, because there are fewer five-letter words close to each other. BLACK and WHITE differ in all five positions, so the minimum is 5. Here's an 8-step solution:

BLACK, SLACK, STACK, STALK, STALE, SHALE, WHALE, WHILE, WHITE.

Follow the A in the third position. It survives all the way from BLACK to WHALE, and only changes to I near the end. Meanwhile the first two letters change from BL to SL to ST to SH to WH. Those consonant pairs are the "detour" that makes room for a path. Every word in this ladder appears in the five-letter word list used by Princeton University's algorithms course, which we checked them against.

Why some word ladders need extra steps

The idea from Step 1 deserves a closer look, because it's the most useful bit of math in the whole puzzle.

Count the positions where the start and target words differ. Computer scientists call this the Hamming distance between the two words. Every step of a ladder changes exactly one position. So if four positions are wrong, you need at least four steps to fix them all. You can never do better than the Hamming distance. You can do worse, though, if some position has to change twice, as the third letter did in HEAD to TAIL.

That gives you a simple test. If your ladder's step count equals the Hamming distance, it's the shortest possible. If it's longer, there might be a shorter one, or there might not, depending on which words exist.

Here's how our verified ladders compare:

Start to target	Positions that differ (minimum)	Steps in our ladder	Provably shortest?
CAT to DOG	3	3	Yes
LEAD to GOLD	3	3	Yes
COLD to WARM	4	4	Yes
LESS to MORE	4	4	Yes
MIND to BODY	4	4	Yes
HATE to LOVE	3	4	Not proven
EYE to LID	3	4	Not proven
HEAD to TAIL	4	5	Not proven
APE to MAN	3	5	Not proven
WET to DRY	3	5	Not proven
BLACK to WHITE	5	8	Not proven
FOUR to FIVE	3	7	Not proven

"Not proven" doesn't mean our ladder is bad. It just means the simple counting test can't confirm it's the shortest. To be sure, you'd have to check every possible path, which is exactly the job computers are good at.

There's one more case worth knowing: sometimes there's no ladder at all. Some words have no neighbors at all: change any one letter and you never get another real word. Donald Knuth, the Stanford computer scientist, called words like that "aloof," a term Jon McLoone borrows in his Wolfram blog post on the longest word ladders. Using Wolfram's dictionary, McLoone counted 817 aloof five-letter words and 2,756 aloof six-letter words. Longer words are lonelier, which is why most word ladders use three, four or five letters.

Word ladders as a graph: how computers find the shortest path

Here's a neat way to picture every possible word ladder at once. Write every word of a given length on a giant sheet of paper. Then draw a line between any two words that differ by one letter. What you get is called a graph: a set of points (the words) connected by lines (the one-letter changes).

In that picture, a word ladder is just a route along the lines from one point to another. And the shortest word ladder is the shortest route. That turns a word puzzle into a classic computer science problem.

Princeton University's algorithms course by Robert Sedgewick and Kevin Wayne uses exactly this as a programming exercise. Students write a program that reads a list of five-letter words and prints a shortest ladder between two of them, where two words are connected if "they differ in exactly one letter." The course's example connects GREEN to BROWN:

GREEN, GREET, GREAT, GROAT, GROAN, GROWN, BROWN.

That's 6 steps, even though GREEN and BROWN only differ in three positions. The program finds it with breadth-first search (BFS). BFS works like ripples in a pond:

1. Start at the first word. Find all its neighbors (words one letter away). These are "1 step away."
2. Find all the neighbors of those words that you haven't seen yet. These are "2 steps away."
3. Keep going, one ring at a time, until the target word shows up.
4. The first time the target appears, you've found a shortest ladder. Trace back through the rings to read it off.

The Princeton course notes that BFS always finds a path with the fewest possible steps, and it does so in time proportional to the number of words plus the number of connections. That's fast. Even with thousands of words, a computer solves a ladder in a blink.

The course also shares a clever trick for building the graph. Instead of comparing every word to every other word, sort the word list. Words that differ only in their last letter, like STALE and STALK, end up next to each other in the sorted list. Then shift the letters around and sort again to catch words that differ in other positions.

The longest word ladders

Once you have the graph, you can ask a fun question: which two words are the farthest apart, where "distance" means the shortest ladder between them? In his 2012 Wolfram post, McLoone searched for exactly that. With his first dictionary, the longest shortest ladder he found ran between the six-letter words CHARGE and COMEDO, and the solution he later posted lists 50 words from start to finish. When he switched to a larger dictionary that included plurals and verb forms, the record became a 46-word ladder between two seven-letter words.

He also revisited Carroll's own challenge of evolving MAN from APE. With a modern word list, the program found a five-step answer: APE, APT, OPT, OAT, MAT, MAN. We checked it: every step changes exactly one letter. Since APE and MAN differ in all three positions, the minimum is 3, so five steps is good but leaves room to wonder.

How to make your own word ladder puzzle

Making a word ladder is easier than you'd think, and it's a good way to build vocabulary. Here's a simple process.

1. Pick a theme pair. Opposites work beautifully, as long as they're the same length: COLD and WARM, WET and DRY, LESS and MORE, HATE and LOVE. So do pairs that tell a little story: SEED to TREE, or LEAD to GOLD.
2. Check the lengths match. Both words need the same number of letters.
3. Solve it yourself first. Use the method above. Write down your solution.
4. Check every rung. Make sure each step changes exactly one letter in the same position, and that every word is real and family-friendly.
5. Decide how much help to give. For beginners, print the right number of blank rungs. For experts, just give the two words and ask for the shortest ladder.
6. Add clues if you like. A clued ladder gives a hint for each rung, such as "a small duck" for TEAL. That turns it into a mini crossword.
7. Make an answer key. Put your solution on a separate sheet. Mention that other answers may exist, and that any valid chain of the same length should count.

That last point matters. Unlike a crossword, a word ladder often has several correct answers. Our guide on how to make an answer key has tips for handling puzzles with more than one right answer.

A clued ladder example

Here's LESS to MORE with a clue for each step (each word is one letter different from the one before):

1. LESS: the starting word
2. Something you suffer when you lose: LOSS
3. To misplace or fail to win: LOSE
4. Traditional knowledge passed down, as in "folk ___": LORE
5. The opposite of less: MORE

Word ladders for students, families and word lovers

Word ladders fit a lot of settings because the rule takes ten seconds to explain and the puzzles scale from very easy to very hard.

• Spelling practice. A three-letter ladder like CAT, COT, COG, DOG has a child look closely at each letter and its sound. It pairs well with a word search built from the same words; see our page on spelling words word searches.
• Vocabulary building. Harder ladders bring in words like GOAD, BOOR and GROAT. Looking them up is half the fun. A themed vocabulary crossword makes a good companion.
• English learners. Word ladders highlight how one letter changes both the sound and the meaning of a word, which can be eye-opening for people learning English. Our page on puzzles for ESL has more ideas for language learners.
• Quick warm-ups. A single ladder fits on an index card and takes a few minutes, which makes it a handy filler. Our list of puzzles for early finishers has more short activities.
• Family game night. Give everyone the same pair of words and three minutes. Shortest valid ladder wins. Ties go to whoever used the most interesting word.

Word ladder variations

Once the classic game feels easy, try one of these twists.

Variation	Extra rule	Example step
Classic (Carroll's Doublets)	Change one letter, same length	COLD to CORD
Add or drop a letter	You may also add or remove one letter	BROW to BROWN
Anagram step	You may also rearrange all the letters as one step	DOG to GOD
Clued ladder	Each rung has a crossword-style clue	"Small duck" = TEAL
Fixed length	You must use exactly a given number of steps	HATE to LOVE in exactly 4
Theme ladder	Every link must fit a theme, like animals or food	CAT, COT, COG, DOG (two animals at the ends)
Race	Two players, same pair, first valid ladder wins	Any pair

The add-or-drop variation is mentioned in the Princeton course too, as a harder programming challenge: words of different lengths become neighbors when the shorter word is the longer word minus its last letter, as in BROW and BROWN. The anagram variation pairs well with our article on anagram solver uses.

Try it yourself: word ladder puzzles with answers

Here are ten ladders to try, from easy to tough. The "Steps" column tells you how many steps our solution uses. Try to match it, or beat it if the minimum is lower. Answers are in the next table, so cover it up first.

Puzzle	Start	Target	Steps in our answer	Minimum possible
1	CAT	DOG	3	3
2	LEAD	GOLD	3	3
3	EYE	LID	4	3
4	HATE	LOVE	4	3
5	MIND	BODY	4	4
6	PIG	STY	5	3
7	WET	DRY	5	3
8	WARM	COOL	5	4
9	POOR	RICH	6	4
10	HAND	FOOT	6	4

Answers

Puzzle	One verified solution
1	CAT, COT, COG, DOG
2	LEAD, LOAD, GOAD, GOLD
3	EYE, DYE, DIE, DID, LID
4	HATE, DATE, DOTE, DOVE, LOVE
5	MIND, BIND, BOND, BONY, BODY
6	PIG, WIG, WAG, WAY, SAY, STY
7	WET, SET, SAT, SAY, DAY, DRY
8	WARM, WORM, WORD, WOOD, WOOL, COOL
9	POOR, BOOR, BOOK, ROOK, ROCK, RICK, RICH
10	HAND, HARD, LARD, LORD, FORD, FORT, FOOT

If you found a different chain with the same number of steps, it's just as correct. And if you found a shorter one, congratulations: you've beaten our answer key. A few notes on the trickier ones:

• Puzzle 5 (MIND to BODY) is a perfect ladder: four positions differ and it takes four steps. BONY is the clever rung.
• Puzzle 6 (PIG to STY) uses the vowel-and-Y trick. WAY, SAY and STY all end in Y, which acts like a vowel there.
• Puzzle 9 (POOR to RICH) wanders through the double-O family (BOOR, BOOK, ROOK) before switching to ROCK.
• Puzzle 10 (HAND to FOOT) leans on the -ORD family (LORD, FORD), a common bridge between words.

Strategy by word length

The length of the words changes the feel of the puzzle more than anything else. Here's what to expect at each size.

Three-letter ladders

Three-letter words are packed tightly together. Almost any consonant-vowel-consonant word has a dozen neighbors, so you rarely get truly stuck. The challenge is finding the shortest ladder, not any ladder. Because there are only three positions, the minimum is never more than 3, and many pairs can hit it. A good habit: fix the vowel early, since the middle letter controls which word families are open to you. CAT, COT, COG, DOG works because the O arrives first and stays.

Four-letter ladders

Four letters is the sweet spot for most players. There are plenty of words, but not so many that every path works. Watch for "families" that share three letters, such as -ORD (CORD, FORD, LORD, WORD), -OOL (COOL, FOOL, POOL, TOOL, WOOL) or -AND (BAND, HAND, LAND, SAND, WAND). Families are bridges: once you're inside one, you can swap the first letter freely to line up with your target.

Five-letter ladders

Five-letter words are spread out, and some have no neighbors at all. Expect detours, like the trip through STACK, STALK and SHALE on the way from BLACK to WHITE. Two tips help here. First, keep consonant blends in mind (BL, SL, ST, SH, WH, GR, BR), since swapping one letter of a blend often makes a new word. Second, work from both ends at once. Write the start word at the top of the page and the target at the bottom, and grow lists of neighbors from each end until they meet.

Six letters and up

At six letters and beyond, ladders get long and sometimes impossible. These make good challenges for experienced solvers and a fun project for anyone learning to program, since a computer search can tell you instantly whether a path exists.

Common word ladder mistakes

• Changing two letters at once. It's the most common slip, especially when you're excited to be close. Say each step out loud: "I changed the second letter only."
• Moving letters around. DOG to GOD isn't a ladder step in the classic game, since letters must stay in place.
• Using non-words. If you're not sure a word is real, look it up before you rely on it.
• Ignoring letters that already match. If a letter is already correct, try hard not to touch it. Every time you change a correct letter, you add at least one extra step to change it back.
• Giving up on a vowel too early. Try all five vowels (and Y) in a stuck position before deciding it's a dead end.
• Forgetting the floor. If your ladder already matches the number of differing positions, stop searching. It can't get shorter.

Make word puzzles to go with your ladders

Word ladders work well alongside other word puzzles on a printed sheet. Use the words from your ladder (or the rungs from the answer key above) as a word list for a companion puzzle.

Our free puzzle maker lets you type your own words or pick a theme, choose a puzzle type, and print it with an answer key. Pair a word search of ladder words with a couple of blank ladders, and you've got a word-play page for a classroom, a club or a rainy afternoon at home.

Three-, Four-, Five- and Six-Letter Ladders Compared

The length of the words changes the feel of the puzzle more than anything else. This table compares what to expect at each size.

Word length	What to expect	Helpful tip
Three letters	Words are packed tightly and you rarely get stuck, so the challenge is finding the shortest ladder	Fix the vowel early, since the middle letter controls which word families are open to you
Four letters	The sweet spot for most players, with plenty of words but not so many that every path works	Watch for families that share three letters, like -ORD, -OOL and -AND, and swap the first letter to line up with your target
Five letters	Words are spread out, some have no neighbors at all, and you should expect detours	Keep consonant blends in mind and work from both ends at once until the neighbor lists meet
Six letters and up	Ladders get long and sometimes impossible, which makes them good challenges for experienced solvers	A computer search can tell you instantly whether a path exists

Frequently Asked Questions

What is a word ladder puzzle?

A word ladder is a puzzle where you change one word into another, one letter at a time, making a real word at every step. For example, CAT becomes DOG through CAT, COT, COG, DOG. The words stay the same length, and each letter keeps its position, so you can't rearrange letters. The usual goal is to reach the target word in as few steps as possible. Lewis Carroll popularized the puzzle in 1879 under the name Doublets, and it's also called a word chain, laddergram or word golf.

Who invented the word ladder?

Lewis Carroll, the pen name of Oxford mathematician Charles Lutwidge Dodgson, is credited with the word ladder. He introduced it as a new puzzle in the magazine Vanity Fair and published a booklet called Doublets, a Word-Puzzle in 1879. His most famous example turns HEAD into TAIL in five steps: HEAD, HEAL, TEAL, TELL, TALL, TAIL. Carroll called the two given words the Doublet, the words in between Links, and the whole series a Chain. He kept experimenting with similar ideas, including a puzzle he planned to call Syzygies.

What are the rules of a word ladder?

Start with the first word and change exactly one letter to make a new real word. Repeat until you reach the target word. Every word must be the same length, and letters can't be swapped or rearranged; each one stays in its own position. Most players don't allow proper nouns or abbreviations, and Carroll asked that words be suitable for polite company. Before playing with others, agree on which dictionary or word list counts, since rare words can cause arguments. Fewer steps is a better score.

How do you solve a word ladder quickly?

First, compare the two words letter by letter and count how many positions differ. That's the fewest steps possible. Lock in any letters that already match. Change the most flexible letters first, often the first letter, and try every vowel in a stuck position, since vowels open up new word families. If you get stuck, work backward from the target by listing words one letter away from it. Keep a note of dead ends so you don't go in circles, then look for shortcuts once you have any solution.

How do I know if my word ladder is the shortest?

Count the positions where the start and end words differ. Each step can only fix one position, so you can never finish in fewer steps than that number. If your ladder uses exactly that many steps, it's guaranteed to be the shortest. If it uses more, a shorter ladder might exist, or it might not, because the in-between words may not exist. To be completely sure, you'd need to check every possible path, which is what a computer search called breadth-first search does very quickly.

What is the hardest word ladder?

Difficulty depends on how far apart two words are in the network of real words. Five-letter and longer words are much harder because fewer of them are one letter apart. In a 2012 analysis on the Wolfram blog, Jon McLoone searched computer word lists for the longest shortest ladders. With his first dictionary, the longest one ran between the six-letter words CHARGE and COMEDO, with 50 words in the posted solution. Some words can't be laddered at all because no single-letter change makes another real word.

Are word ladders good for kids learning to read and spell?

Word ladders are a natural fit for spelling and vocabulary practice, because each step makes you look closely at one letter and think about how it changes the word's sound and meaning. Simple three-letter ladders like CAT, COT, COG, DOG work for beginning readers, while four- and five-letter ladders bring in less common words worth looking up. They're quick, need only a pencil, and have more than one right answer, which makes them friendly for groups. Pair them with word searches or crosswords that use the same words.

Can you add or remove letters in a word ladder?

Not in the classic version. Lewis Carroll's Doublets keeps every word the same length and lets you change only one letter at a time. Some modern variations do allow adding or dropping a letter as a step, so BROW could become BROWN. Princeton University's algorithms course even suggests this as a harder programming exercise. Another variation lets you rearrange all the letters as one move, turning DOG into GOD. If you play a variation, say so at the start so everyone follows the same rules.

How do computers solve word ladders?

A computer treats every word as a point and draws a line between any two words that differ by one letter. That structure is called a graph, and a word ladder is a route through it. To find the shortest ladder, programs use breadth-first search. It finds all words one step from the start, then all words two steps away, and so on, ring by ring, until the target appears. The first time the target shows up, the program has found a shortest ladder, often in a fraction of a second.

Sources

We checked every source below while writing this guide. Last reviewed October 30, 2026, by Joan Ramos.

1. Doublets, a Word-Puzzle (Lewis Carroll, 1879; digitized from Oxford University's copy) (Google Books)
2. Lewis Carroll in Wonderland and at Home: The Story of His Life (Belle Moses, 1910) (Project Gutenberg)
3. The Life and Letters of Lewis Carroll (Stuart Dodgson Collingwood, 1899) (Project Gutenberg)
4. Algorithms, 4th Edition, Section 4.1: Undirected Graphs (word ladder exercises) (Princeton University)
5. The Longest Word Ladder Puzzle Ever (Jon McLoone, 2012) (Wolfram Research)