What Is Samurai Sudoku? The 5-Grid Puzzle Explained

If you've come across the term "samurai sudoku" — or seen a puzzle that looks like five sudokus glued together in an X — and wondered what you're looking at, here's the clear answer. Samurai sudoku is a sudoku variant built from five overlapping 9x9 grids, which is why it's sometimes called 5-grid sudoku or 5-sudoku-in-one. It keeps every rule of ordinary sudoku and adds a single twist: the grids share corners, and those shared regions tie the whole thing into one connected puzzle. This explainer walks through the structure piece by piece so the layout finally makes sense.

Want to try one while you read? Open a samurai sudoku in another tab.

The short definition

Samurai sudoku is a number puzzle made of five standard 9x9 sudoku grids arranged so that one central grid overlaps with four corner grids. Each corner grid shares exactly one 3x3 box with the center. You solve it the same way as regular sudoku — every row, column, and 3x3 box of each grid must contain the digits 1 to 9 without repeating — with the added condition that the shared boxes must be valid in both grids they belong to.

That's it. Five sudokus, joined at four corners, solved as one.

How the five grids fit together

Picture an X, or a quincunx (the five-dot pattern on a die):

• One grid in the center.
• Four grids in the corners — top-left, top-right, bottom-left, bottom-right.
• Each corner grid's inner 3x3 box is the same 3x3 box as one of the center grid's outer boxes.

Those four shared boxes are the only places the grids touch. Everything else is independent. Between the corner grids there are gaps — empty space where no cells exist — which is why a samurai sudoku looks like a plus sign or an X rather than a solid square.

Why it's called "5 grid sudoku" and "5 sudoku in one"

The alternative names are just literal descriptions. "5 grid sudoku" and "5 sudoku in one" both point at the obvious: there are five complete sudoku grids in a single puzzle. "Overlapping sudoku" describes the mechanic — the grids overlap. And "samurai sudoku," the most common name, comes from the puzzle's shape resembling a samurai's crest or helmet emblem. They all refer to the same five-grid layout.

How big is it?

A single sudoku has 81 cells. Five would be 405 — but because the four corner grids each share a 3x3 box (9 cells) with the center, those overlaps are counted once, not twice. So the total is:

5 × 81 − 4 × 9 = 369 cells.

That's why the board feels so much larger than a regular sudoku: it's more than four and a half times the cells, laid out across a 21×21 area with four empty corners.

How it differs from regular sudoku

The difference is structural, not logical. The rules of each individual grid are identical to regular sudoku — the same one-of-each constraint on rows, columns, and boxes. What's new is:

1. There are five grids, not one.
2. They share boxes, so a digit in an overlap must satisfy two grids at once.

The shared boxes are also what make the puzzle solvable as a whole — they let progress in one grid unlock the next. We cover that solving mechanic in the overlap trick, and a fuller head-to-head in samurai sudoku vs regular sudoku.

Is it hard?

Not as hard as the size suggests. Because the logic per cell is ordinary sudoku, an easy samurai sudoku is very approachable — it just takes longer to fill 369 cells. The shared boxes can even make parts of it easier, since those cells obey six constraints (three from each grid) and are often the simplest to pin down. The challenge is endurance and keeping five grids straight, not difficult individual deductions.

Try it for yourself

Now that the structure makes sense, the best next step is to solve one. Start with an easy samurai sudoku to get the feel of the overlaps, or read the step-by-step beginner guide first. If you like it, the wider family of sudoku variants has plenty more overlapping puzzles to explore.

Frequently asked questions

What is samurai sudoku?

Samurai sudoku is a sudoku variant made of five overlapping 9x9 grids — one in the center and four in the corners, each sharing a 3x3 box with the center. You solve each grid by normal sudoku rules, with shared-box cells needing to be valid in both grids they belong to.

How many grids are in a samurai sudoku?

Five: one central grid and four corner grids. Each corner grid overlaps the center by one shared 3x3 box, and those four overlaps are what connect the five grids into a single puzzle.

Why is it called samurai sudoku?

The name comes from the puzzle's shape, which resembles a samurai's crest or helmet emblem. It's also known as 5-grid sudoku, 5-sudoku-in-one, or overlapping sudoku, all describing the same five-grid layout.

How many cells does a samurai sudoku have?

369 cells. Five 9x9 grids would total 405 cells, but the four shared 3x3 boxes (9 cells each) are counted once instead of twice, giving 5 × 81 − 4 × 9 = 369.

Is samurai sudoku the same as overlapping sudoku?

Samurai sudoku is the most popular type of overlapping sudoku — specifically the five-grid version. "Overlapping sudoku" is a broader term that also covers other layouts, like the two-grid twin or larger arrangements such as butterfly and gattai variants.