How a crossword grid works

A crossword grid is a set of rules made visible. Before you read a single clue, the pattern of black and white squares has already told you how long every answer is, which letters you will be handed for free, and where the puzzle is likely to fight back. Learning to read a grid takes about ten minutes and pays for itself in every puzzle after that.

The shape is not decorative

Almost every published daily crossword in English uses 180 degree rotational symmetry. Turn the page upside down and the black squares land exactly where they were. Editors require it, so setters design around it. The practical consequence for a solver is that grids are predictable. If the top left corner is open and airy, the bottom right corner will be too, and the long entries usually arrive in matched pairs.

Sizes are equally settled. An American daily is 15 by 15. The Sunday puzzle is 21 by 21, which makes it longer rather than harder. A British blocked daily is normally 15 by 15 as well.

Two grid traditions

American grids are fully checked. Every white square belongs to one across answer and one down answer, so every letter is tested twice. The minimum entry length is three letters and two letter entries are not permitted. The result is a dense grid with comparatively few black squares, which is exactly why the same short vowel heavy words keep turning up.

British grids, particularly cryptic ones, use a lattice: more black squares, longer entries, and alternating checked and unchecked squares. Roughly half the letters in a typical entry sit in squares that no other answer touches. That is a deliberate trade. You get less help from the crossings, so the clue has to be solvable on its own, which is precisely what cryptic wordplay provides.

How the numbering works

Numbers mark positions, not difficulty. Work left to right along each row, then drop to the next row. A white square takes the next number if it begins an across entry, a down entry, or both. That is why 1 Across and 1 Down almost always share the same top left square.

Gaps in the sequence are normal. If a puzzle has no 13 Across, it is because 13 numbers a square that starts a down entry only. Beginners sometimes read a missing number as a misprint. It is the system working correctly.

Checked and unchecked squares

A checked square is one where two answers cross, so its letter is confirmed from two directions. An unchecked square, often shortened by British solvers to an unch, carries a letter that only one answer supplies. Both terms, and the rest of the vocabulary this course uses, are collected in the glossary.

The distinction should change your behaviour. In a fully checked grid a wrong answer is loud: it breaks four or five crossing entries and you find it quickly. In a grid with unchecked squares a wrong answer can sit there quietly for twenty minutes, because nothing in the puzzle contradicts it.

Why crossings do the work

Take a five letter slot you cannot define your way into. With no letters at all the field is enormous. One crossing gives you something like _ _ E _ _, which still allows thousands of words. A second gives you _ R E _ _, and now you are choosing among a few dozen candidates: PREEN, TREAT, FRESH, CREST, DREAM. A third letter usually settles it.

Short slots resolve fastest, because each crossing removes a larger share of the field. A four letter slot with two known letters, say _ L _ E, is down to a handful at once: BLUE, FLEE, GLEE, SLOE. This is why experienced solvers hunt for the corner holding the most letters rather than the clue they like the look of. That working order is set out in solve the crossings first.

Read the grid before clue one

Thirty seconds spent reading the grid changes where you start, which changes how the whole solve goes.

These conventions have been stable for a long time. The first known crossword, published by Arthur Wynne in 1913, was diamond shaped and fully checked, and the symmetry rules settled soon afterwards. A general history sits in the Wikipedia article on crosswords, while grid statistics for individual published puzzles, including black square counts and word counts, are archived at XWord Info.