Sumdoku, Sum Sudoku & Killer Sudoku: Why It Has So Many Names

If you've come across "sumdoku," "sum sudoku," or "addition sudoku" and wondered whether they're different puzzles, here's the quick answer: they're all the same puzzle, the one most people now call killer sudoku. One game, a pile of names — and each one tells you a little about where the puzzle came from and how it spread. This article untangles the aliases so you know exactly what you're playing, whatever a given site happens to call it.

Want to just play it under any name? It's right here at killer sudoku.

They're all the same puzzle

Whatever the label, the rules are identical: a 9x9 grid split into outlined cages, each with a target sum, where the digits in a cage must add to that sum without repeating, and every row, column, and 3x3 box still holds 1 through 9 once. If a puzzle has cages with sums in the corners, it's killer sudoku — no matter what name sits at the top of the page. (New to the rules? The killer sudoku rules page lays them out.)

So why the naming chaos? Because the puzzle traveled across countries and publishers, and each one reached for a name that made sense to its audience.

Sumdoku

"Sumdoku" is a portmanteau of sum and sudoku, and it's used by several apps and websites — often to sound a little friendlier and less violent than "killer." The name highlights the defining feature: you're working with sums. If you searched for "sumdoku free online," you were looking for exactly this puzzle, just under its gentler branding.

Sum sudoku and addition sudoku

"Sum sudoku" and "addition sudoku" are the most literal descriptions of all — they tell you straight out that the puzzle is sudoku where you add numbers. These names are common in educational settings and puzzle books aimed at newcomers, precisely because they're self-explanatory. Nobody has to wonder what an "addition sudoku" involves.

Samunamupure: the original name

The puzzle's roots trace to Japan, where it was published under the name samunamupure, derived from the English phrase "sum number place." ("Number Place," or nanpure, is the original Japanese name for what the West calls sudoku.) So the literal translation is something close to "sum number place" — which is, once again, exactly what the puzzle is. We dig into this story in the history of killer sudoku.

So where did "killer" come from?

The "killer" name took hold in the English-speaking world, particularly after the puzzle gained popularity in UK newspapers in the mid-2000s, riding the wave of the global sudoku craze. "Killer" sells the difficulty — it signals a tougher challenge than standard sudoku, which is a fair warning given the blank starting grid. It's now the dominant name in English, which is why most sites (including this one) lead with it.

A quick glossary

Here's every name you're likely to meet, all pointing to the same puzzle:

• Killer sudoku — the dominant English name, emphasizes difficulty.
• Sumdoku — a friendly sum + sudoku blend, common in apps.
• Sum sudoku — literal description, popular in puzzle books.
• Addition sudoku — the most beginner-friendly label, common in education.
• Samunamupure — the original Japanese name ("sum number place").
• Sums sudoku / cage sudoku — occasional variants you'll see in the wild.

Does the name change how you play?

Not at all. The strategy is the same regardless of the label on the box. Lock the obvious cages, lean on the 45 rule, and filter combinations as you place digits — that approach works whether the site says "killer," "sumdoku," or "sum sudoku." If you want the full method, the killer sudoku strategy guide covers everything.

The takeaway: don't let the names confuse you. They're all doorways into the same satisfying puzzle. Pick whichever one your favorite site uses, and start solving.

Frequently asked questions

Is sumdoku the same as killer sudoku?

Yes. Sumdoku is just another name for killer sudoku — a sudoku grid with outlined cages whose digits must add to a target sum without repeating. The "sumdoku" name (a blend of sum and sudoku) is mainly used by certain apps and sites to sound friendlier than "killer."

What is sum sudoku?

Sum sudoku is another name for killer sudoku, emphasizing that you work with cage sums. It's the same puzzle: fill the grid so each row, column, and box has 1 to 9, and each cage's digits add to its printed sum without repeating.

Why is it called killer sudoku?

The "killer" name became popular in English-language newspapers in the mid-2000s and signals a tougher challenge than standard sudoku, mainly because the grid usually starts with no given numbers. It's now the most common name in English.

What is samunamupure?

Samunamupure is the original Japanese name for killer sudoku, derived from "sum number place" — number place being the original Japanese term for sudoku itself. It's where the puzzle's modern forms originate.

Are sumdoku and killer sudoku played the same way?

Exactly the same. The name doesn't change the rules or the solving techniques. Lock the obvious cages, use the 45 rule, and filter combinations — the approach is identical whatever the puzzle is called.