What is Shikaku?
A simple rule. An elegant puzzle.
Support shikaku.ch
Shikaku.ch is free for everyone — no ads, no subscription. If you enjoy the daily puzzle, any support means a lot.
The puzzle
Shikaku (四角に切れ) is a Japanese logic puzzle originally published by Nikoli — the same company that introduced Sudoku to the world. The name roughly translates to "divide by box."
The rules are simple: you are given a grid with numbers scattered across it. Your goal is to divide the entire grid into non-overlapping rectangles, so that each rectangle contains exactly one number — and that number equals the rectangle's area.
A cell with the number 6 must belong to a rectangle of area 6: for example 1×6, 2×3, or 3×2. A cell with 1 is a rectangle all by itself. Every cell in the grid must belong to exactly one rectangle.
How to play
- Look at the numbers on the grid — each one is a clue telling you the area of its rectangle.
- Drag across cells to draw a rectangle. The rectangle must have an area equal to the number inside it.
- Click a single cell to place a 1×1 rectangle (for clues with the number 1).
- Click an existing rectangle to remove it. Right-click also erases.
- The puzzle is solved when every cell is covered and all rectangles are correct.
Want to improve? Read the full Shikaku strategy guide →
Frequently asked questions
Is Shikaku free to play?
Yes — completely free, no account needed, no app to download. A new daily puzzle is published every day at midnight, the same for everyone worldwide. You can also play unlimited puzzles in four grid sizes: 5×5, 10×10, 20×20, and 25×25.
How hard is Shikaku?
Shikaku scales well with grid size. A 5×5 puzzle takes most people under a minute. A 25×25 expert grid can take 20–30 minutes of focused solving. The daily puzzle uses a 10×10 grid — a good challenge for most players without being overwhelming.
Is there a Shikaku app?
Shikaku.ch works in your phone's browser without any app. Just open the site on your phone and it works like an app — you can even add it to your home screen from your browser's share menu.
Where does Shikaku come from?
Shikaku was invented in Japan by Nikoli, a puzzle publishing company in Tokyo. Nikoli is also responsible for popularising Sudoku internationally. Shikaku has been published in puzzle magazines since the early 2000s.
What are other names for Shikaku?
Shikaku is also known as Shikaku ni Kire, Rectangles, Box Up, and Divide by Squares. The underlying puzzle is the same regardless of the name. LinkedIn's Patches puzzle is a close cousin — read how they compare →
About this site
Shikaku.ch is a small side project. I built it because my blockkurs was not as interesting as I hoped. The site is still a work in progress, and I'm continuously improving it. If you have feedback, I appreciate every message.
Impressum
Responsible for this website:
Juulian
St. Gallen, Switzerland
www.juulian@gmail.com
This website is a private project. All content is provided for informational and entertainment purposes.
Ready to try it? A new puzzle is waiting for you every day.
Play today's puzzle →Privacy policy
Last updated: March 2026
Analytics. This site uses Google Analytics to understand how many people visit and which pages are most popular. Google Analytics collects anonymised data including your approximate location (country/city), device type, and pages visited. Your full IP address is not stored. You can opt out using the Google Analytics opt-out browser add-on.
Advertising. This site uses Google AdSense to display ads. AdSense may use cookies to show you personalised ads based on your browsing activity. You can opt out of personalised ads at google.com/settings/ads. For more information see Google's advertising policy.
Local storage. The site saves your daily puzzle streak, best time, and number of solved puzzles in your browser's local storage. This data never leaves your device and is not sent to any server.
No data sold. Shikaku.ch does not sell any data to third parties.
Contact. For any questions about this privacy policy, email www.juulian@gmail.com.