Word Ladder Solver

Enter a start word and an end word of the same length. The solver changes one letter at a time and lists every shortest ladder between them, so you can pick the route you like. Works with three, four, and five letter words.

Three to five letters
Breadth-first search
Every shortest path

Solve a Ladder

Line illustration of a person holding a magnifying glass up to a ladder of blank letter tiles, with one tile highlighted in each row to trace a path down the stack

Worked word ladder examples

Each ladder below was produced by this solver and checked step by step. The label above each one says how many different ladders share that same shortest length.

3 letters, 3 moves, 2 shortest ladders
CAT → COT → COG → DOG
3 letters, 4 moves, 11 shortest ladders
DAY → DAD → DUD → DUN → SUN
4 letters, 4 moves, 3 shortest ladders
COLD → CORD → WORD → WORM → WARM
4 letters, 5 moves, 8 shortest ladders
HEAD → HEAR → HEIR → HAIR → HAIL → TAIL
5 letters, 5 moves, 4 shortest ladders
WITCH → WINCH → WENCH → TENCH → TEACH → PEACH
5 letters, 8 moves, 14 shortest ladders
BLACK → SLACK → STACK → STALK → STALE → SHALE → WHALE → WHILE → WHITE

How the word ladder solver picks each move

Every word list on this page is a map. Each word is a place, and two places are joined when they differ by exactly one letter. WARM, for instance, joins ten words in the four letter list.

WARM at the centre of a ring of the ten words one letter away from it: FARM, HARM, WARD, WARE, WARN, WARP, WARS, WART, WARY and WORM.

That short list is everything the solver has to choose from at each rung. The solver works outward in rings: every word one move from your start, then every word two moves out, and so on. The first ring to contain your end word is the answer, and by then nothing shorter can have been missed.

Choosing well is harder than it looks, because a single letter change can only do one of three things. It moves you one step nearer the end word, one step further away, or leaves the distance untouched. Take COLD to WARM, four moves, one of the worked examples above. COLD has twelve legal moves:

The twelve words one letter from COLD, sorted by what each move costs on the way to WARM. CORD keeps the ladder at four moves. BOLD, COED, COLE and FOLD cost one move. COLA, COLT, GOLD, HOLD, MOLD, SOLD and TOLD cost two.

Only CORD keeps the ladder at four. Four moves cost you a step, and seven of the twelve walk away from WARM entirely. GOLD and HOLD feel like obvious moves and are among the worst available. This is the gap the solver closes: it can see which of the twelve is the one, and you cannot, because seeing it means knowing the distance from every one of those words to WARM.

Why word ladder length changes the puzzle

The three word lists behind this word ladder solver do not behave alike, and the difference is not the one people expect. The five letter list is the biggest by far, and it is also the emptiest.

Three histograms sharing one axis, showing how many one letter neighbours a word has in each list. Three letter words cluster to the right with many neighbours, four letter words spread evenly, five letter words pile up at zero, one and two.

A three letter word has about twelve ways out on average. A five letter word has under five, and the most common count is three. The five letter list holds 5,010 words against 654 for three letters, so it is 7.7 times the size with a third of the connections per word. Longer words are rarer in every direction at once, and a word ladder needs those directions.

That thinning has a consequence you can see the moment a solver search fails.

Three bars, one per word list, split into the groups of words that can reach each other. The three and four letter lists are effectively one block each. The five letter list splits into a large block, a band of small groups, and 654 words with no neighbours at all.

The four letter list is a single connected block, so any two words in it have a ladder between them. The five letter list breaks into 825 separate groups, and 654 of its words have no partner within a single change. When this word ladder solver reports that no ladder connects your two five letter words, that is the map talking, and changing one of the two words usually finds a route.

When several word ladders tie, and when your puzzle names a step count

The shortest word ladder is rarely a single answer. HEAD to TAIL takes five moves, and there are eight different five move ladders. The choice widens to three words in the middle and closes again at the end:

HEAD to HEAL, HEAR or HELD, then on through three more forks to TAIL.

Pick the first route out of a search and you have taken one of those eight without being told the other seven existed. This solver lists them all, so the choice of wording stays yours.

The same number answers a question worksheets and puzzle books keep asking. When a puzzle demands a ladder of a set length, solve it here first and read the move count. If your book wants a seven step ladder and the shortest is five, a seven step version has to wander deliberately, and the two extra rungs are yours to place. If the shortest is longer than seven, no seven step ladder exists and no amount of searching will produce one. This word ladder solver takes two words rather than clue text, so it will not fill in a partly completed grid, but the shortest length it returns is the fact those puzzles turn on.

Why this solver

Three, four, and five letters
Most word ladders in books and worksheets are three or five letters long, so the solver covers those as well as four. Each word list loads only when you choose that length.
All shortest paths shown
When several ladders share the same minimum length, the solver lists all of them, up to twenty, so you can choose the route you prefer instead of taking the first one found.
Breadth-first search, so the answer is provably shortest
The solver explores the word graph one layer at a time, which guarantees the ladder it returns is the shortest one that exists. There is no guessing and no heuristic.
Works with any Poople puzzle
Stuck on the daily Poople puzzle? Choose four letters, enter your current word as the start and POOP as the end, and the solver finds the shortest path from where you are.

About the solver

How does the solver work?

The solver uses a breadth-first search across the word graph for the length you chose. It explores all valid one-letter changes from the start word outward until it reaches the end word, which guarantees the path found is the shortest possible.

What word lengths can I use?

Three, four, and five letters. Both words have to be the same length, which is why the length selector sets the size of both boxes. Six letters and up are not offered, and the reason is measurable rather than a matter of taste. We built the six and seven letter lists from the same source and measured them the same way as the answer further down: in a six letter list of about 8,100 words, more than a quarter of the words have no one-letter neighbour at all, and only around 18 percent of random pairs have any ladder between them. At seven letters that falls to roughly 5 percent. Word ladders stop working as a puzzle somewhere between five and six letters, so shipping those lengths would mostly ship dead ends.

Where do the words come from?

Three and five letter ladders use SCOWL size 60, a widely used open word list that is large enough to cover everyday vocabulary while leaving out obscure entries that would make a solved ladder unreadable. You can read the full SCOWL licence on this site. We filter that list before use: words whose dominant meaning is a slur or is sexually explicit are removed, while ordinary vocabulary that a profanity filter tends to flag by mistake is kept. Four letter ladders use Poople’s own dictionary instead, for the reason in the next answer.

Why do four letter ladders use a different word list?

So that four letter results always match what the daily game accepts. Poople’s dictionary holds the four letter words that connect to POOP, which means a handful of ordinary words such as ABLE and ACRE are missing from it. That is a real limitation for general puzzles, and it is the trade for the solver never showing you a word the game would reject.

Does it find every shortest path?

Yes. The solver collects all paths that share the minimum length and lists each one. If the number of equal-length paths exceeds twenty, it shows the first twenty and notes how many were found in total.

What is a word ladder?

A word ladder is a puzzle where you transform one word into another by changing a single letter at each step, keeping a valid word at every rung. Lewis Carroll invented the concept in 1877 under the name Doublets. Poople is a daily word ladder where the target is always POOP.

Why does it say no ladder connects my two words?

Because a word list is not always one connected whole. At five letters in particular, many entries have nothing a single change can reach, and other pairs belong to clusters that never touch. Four letters behaves differently and always finds a route. The article higher up this page measures all three lists and shows what that looks like. In practice, swap one of your two words for a near synonym and search again.

Why would I use a word ladder solver?

When you are stuck on a puzzle, the solver shows the shortest path from where you are so you can get moving again without guessing blindly. It also helps you learn the bridge words that turn up in many shortest paths.

How is this different from other word ladder solvers?

A solver that stops at the first shortest route it finds will hand you one ladder. This word ladder solver keeps going and collects every ladder that ties for the shortest length, then lists them all, so you can pick the wording you like rather than taking whatever came out first. It also covers three and five letter puzzles instead of a single length, and it names the word list behind each length rather than leaving you to guess why a word was rejected.

Play today Practice What is a word ladder Past answers