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Guide

How to Play Shikaku

Shikaku rules in plain English: one clue per rectangle, clue = area, cover the grid. Quick-start steps, named techniques, and FAQ — free to play.

How to Play Shikaku

  1. 1.

    Divide the grid into rectangles and squares along the gridlines.

  2. 2.

    Every rectangle must contain exactly one number.

  3. 3.

    That number equals the rectangle's area — a 6 sits in a rectangle covering exactly 6 cells (1×6, 2×3, 3×2, or 6×1).

  4. 4.

    Rectangles fill the whole board with no gaps and no overlaps.

  5. 5.

    Every puzzle has exactly one solution, so you never need to guess — draw by dragging from one corner of a rectangle to the opposite corner.

Your first board in four steps

Learn the rules in under a minute, then solve your first board.

  1. 1

    Read the numbers

    Each number on the grid belongs to one rectangle, and the number tells you that rectangle's exact area in cells. A 1 is a single cell; a 6 covers six cells.

  2. 2

    Find the forced clues

    Start where only one rectangle can fit: 1s are instant, prime numbers must be thin strips, and clues pressed against an edge or corner have few ways to grow.

  3. 3

    Drag to draw rectangles

    Press on one corner cell and drag to the opposite corner — the preview shows the area live. On touch you can also tap a corner, then tap the opposite corner. The number dims when its rectangle matches.

  4. 4

    Tile the whole board

    Every cell must end up inside exactly one rectangle, each containing one matching number. When the last cell is covered correctly, the board is solved — share your time or jump to the next puzzle.

How do you solve Shikaku without guessing?

Every board here is verified to a single solution and graded by which of these techniques it needs: easy boards fall to the first five, medium boards demand common-cell deduction, and hard boards demand orphan prevention and region logic. When you stall, walk this list top to bottom — one of them always applies. Most of the ladder also carries over to Patches, the LinkedIn-style descendant whose clues name a shape as well as an area; our sister site sets the two rule sets side by side in Patches vs. Shikaku on Patches Game.

Singles

Easy

Some clues have exactly one rectangle that fits. Every 1 is a single cell. A 2 with only one free neighbor is done. Scan for these first — each placement is free information, because its edges become walls for every clue around it.

Forced rectangles

Easy

Look at empty cells, not just clues: if only one clue's possible rectangles can reach a cell, that clue MUST cover it — which usually pins the rectangle's direction or position. Cells hugging walls and corners are the best place to spot this.

Prime clues are strips

Easy

A prime number (2, 3, 5, 7, 11, 13…) can only form a 1×n strip. On a 10-wide board an 11 must run vertically… or not exist; a 7 has just two orientations, and other clues in its row or column often eliminate one of them instantly.

Edge and corner squeeze

Easy

A clue near the board's edge has less room to grow: a 9 in a corner may only fit as a 3×3 square, and a 6 pressed against a wall loses half its shapes. Work the border first — it's where boards unravel.

Clue exclusion

Easy

A rectangle may never contain two numbers. Rule out every candidate that would swallow a neighboring clue — in crowded areas this alone can cut a clue from six candidates to one.

Common-cell deduction

Medium

When every remaining candidate for a clue overlaps on certain cells, those cells belong to that clue no matter which candidate is right. Claim them mentally: no other clue's rectangle may cross them, which forces hands elsewhere. Medium boards require this move.

Orphan prevention

Hard

A placement is wrong if it would strand a cell no remaining rectangle can reach. Before committing a big rectangle, check the cells it walls off — and when you spot an almost-enclosed empty cell, the one rectangle that can still reach it is forced. Hard boards turn on this.

Region decomposition & area parity

Hard

Solved rectangles carve the board into independent regions. The clue areas inside a region must sum exactly to its cell count — if a candidate would split off a region whose clues cannot pay for its cells, that candidate is dead. This closes out the giant boards.

Shikaku FAQ

Shikaku is a Japanese logic puzzle first published by Nikoli in 1989. You divide a grid into rectangles so that each rectangle contains exactly one number, and that number equals the rectangle's area in cells. The rectangles must tile the whole grid with no gaps or overlaps. It's also known as Rectangles, Divide by Box, or Sikaku.

Drag from one corner of a rectangle to the opposite corner to draw it around a number. The number tells you the exact area the rectangle must cover — a 4 needs four cells, as a 1×4 strip or a 2×2 square. Start with forced clues like 1s and prime numbers near an edge, then let each placed rectangle narrow down its neighbors.

Yes — everything on this site is free with no account and no downloads. That includes the daily Shikaku, the full archive of past dailies, and more than 600 puzzles across five board sizes from 5×5 to 20×20. Your progress and streak are saved automatically in your browser.

No. Every puzzle here is machine-verified to have exactly one solution, and our grader confirms each board can be finished by pure deduction. If you're stuck, there is always a forced move on the board — usually a number with only one rectangle that fits, or an empty cell only one rectangle can still reach.

A new daily Shikaku is published every day at midnight US Eastern time, and everyone in the world gets the same board. Miss a day and it isn't lost — every past daily stays playable forever at its own permanent URL in the archive.

Start on 5×5 or 7×7 if you're new — they teach the clue-reading habits everything else builds on, and most solve in a few minutes. The classic Shikaku experience is 10×10. When that feels comfortable, the 15×15 and 20×20 giants offer long, layered solves that can span multiple sittings (your progress autosaves).

Yes — the board is built for touch. Drag your finger from corner to corner to draw a rectangle, or tap one corner and then the opposite corner. Long-press a rectangle to remove it, or simply draw over it to replace it. It works in any modern browser on phones, tablets, and desktops.