The Rules of Fill-In Puzzles: How Word Fit and Number Fit Work
A fill-in puzzle looks like a crossword with no clues: a grid of slots, and a list of words (or numbers) beside it. That's the whole secret — the clues are replaced by a list of everything you need. The rules are simple, and once you know them, every fill-in puzzle in the world is solvable the same way.
The three parts of a fill-in puzzle
- The grid. A rectangle of cells, some filled in solid black. The white cells form runs of connected squares — these are the slots, and each slot runs either across (left to right) or down (top to bottom).
- The list. Every word or number you need, printed beside the grid. Words are grouped by how many letters they have; numbers are grouped by how many digits.
- The numbers. Each slot has a number printed in its first cell, and each entry in the list carries the number of its slot.
The rules, plain and simple
- Every entry is used exactly once. Each word or number in the list belongs in exactly one slot, and every slot is filled by exactly one entry. When you finish, the grid is full and the list is empty.
- Match by length and number. A slot of five cells takes a five-letter word (or a five-digit number). The number printed on an entry matches the number printed at the start of its slot — that's how you know where it goes.
- Crossings must agree. Where an across slot and a down slot cross, they share a cell. The letter (or digit) you place there has to be correct for both entries at once. Crossings are your most powerful hints.
- Black cells are never filled. They're just separators between slots.
Why the rules make the puzzle fair
Because every entry is used exactly once and every slot has exactly one home for it, a fill-in puzzle is guaranteed to be solvable. There are no trick answers and no trivia to know — everything you need is printed on the page. That's why fill-ins are so popular with beginners, kids and language learners: the rules are the same every time, so you can jump straight into solving.
Word fill-in vs. number fill-in
The two versions are the same puzzle with different contents:
- Word fill-in (also called a word fit or fill-it-in) uses words from a theme — animals, food, sports, countries, jobs or nature. Entries are grouped by letter count.
- Number fill-in (also called a number fit or figure fit) uses numbers instead. Entries are grouped by how many digits they have, and the themes change which numbers appear — classic, even, odd, prime or multiples of 3.
Try both: the word fill-in puzzle maker generates fresh word puzzles in six categories, and the number fill-in puzzle maker creates fresh number puzzles with five number themes. Both offer easy, medium and hard levels with printable grids and answer keys.
Tips for your first solve
- Start with the longest entries. They have the fewest possible slots, so they're the easiest to place.
- Count the cells. Before looking for a word, count the length of the slot — then scan the list for entries of that exact length.
- Use the crossings. Once one word is in place, the letters it contributes narrow down the choices for every word that crosses it.
- Work in pencil. If you print a puzzle, a light pencil lets you fix slips as you go. On screen, our tools highlight wrong entries when you check.
Where fill-ins fit in the puzzle family
Fill-ins share their grid logic with crosswords — the crossing letters, the numbered slots — but skip the general-knowledge clues entirely. If you enjoy the fitting-and-logic side but want the challenge of clues, read our comparison of fill-in puzzles vs. crosswords. And for a different kind of number logic, our sudoku generator applies the same "exactly once per line" idea to rows, columns and boxes.
Ready to try one?
Open the word fill-in maker and pick a category and difficulty — a fresh puzzle appears instantly, ready to print or save as a PDF. Prefer numbers? The number fill-in maker is waiting. Now that you know the rules, you're ready to solve.