What is Shikaku?
Shikaku is a quick, visual logic puzzle about areas. The grid is dotted with numbers, and you draw rectangles around them so that each rectangle’s size matches its number exactly. When every cell is covered, you are done.
It is easy to learn and pleasantly tidy to solve. Play Shikaku online free here, from 7×7 warm-ups to big 15×15 grids.
Where Shikaku comes from
Shikaku, which roughly means “divide by squares”, is a puzzle from the Japanese publisher Nikoli. The grid is scattered with numbers, and you divide the whole grid into rectangles so that each rectangle contains exactly one number, equal to its area.
How to play here
Drag from one corner of a rectangle to the opposite corner to draw it. Drag over it again to change it, or draw a new rectangle on top to replace it. A 6 can become a 1×6, 2×3, 3×2 or 6×1 rectangle, as long as it covers no other number and fits in the grid.
A step-by-step way to solve
- Start with big numbers and prime numbers. A prime number like 7 or 11 can only be a single row or column, which often fits only one way.
- Check which number can reach each cell. A cell that only one number can possibly cover must belong to that number’s rectangle.
- Use the corners. Corner cells have few ways to be covered, so they often decide the rectangle next to them.
- Leave the 1s and 2s for last. They are flexible and usually fall into place once the big rectangles are settled.
- Watch for boxed-in areas. If a region of empty cells can only be reached by one number, that number’s rectangle must include it.
Why play Shikaku?
Shikaku is quick to learn and very visual: you watch the grid turn into a neat patchwork of rectangles. It is a good puzzle for building the habit of asking “which clue can reach this cell?”. Next, try Star Battle or Hitori for more region logic.
How to play Shikaku
- Divide the whole grid into rectangles or squares.
- Each rectangle must contain exactly one number.
- That number equals the area of the rectangle, counted in cells.
- Every cell belongs to exactly one rectangle.
Shikaku tips
Big numbers and prime numbers first
A 7 can only be a 1×7 line, and a large number near a wall has few shapes that fit. Place those before the flexible ones.
Check which number can reach a cell
When an empty cell can only be covered by one number's rectangle, that rectangle must stretch to include it.
Use the 1s and 2s last
Small numbers fit almost anywhere, so leave them until the big rectangles have claimed their space.
Frequently asked questions
What does Shikaku mean?
Shikaku is Japanese for square. The puzzle is also called Rectangles or Divide by Box.
Can a rectangle be a single cell?
Yes. A cell with the number 1 is a 1×1 square on its own.
Is there always one solution?
Yes. Each puzzle has one valid way to split the grid.
