One puzzle, two names
If you grew up with puzzle books, you may know this game as cross sums. If you met it more recently, you probably know it as Kakuro. They are the same puzzle. Cross sums is the older English name, used for decades in newspapers and puzzle magazines. Kakuro is the Japanese name, a contraction that travelled worldwide alongside Sudoku in the 2000s and largely stuck.
Why "cross sums" fits
The name describes the puzzle perfectly. Like a crossword, it is a grid of crossing entries. Unlike a crossword, the clue for each entry is a sum, and the answer is a set of digits that adds up to it without repeating. Every white cell sits at the crossing of one across sum and one down sum, which is exactly the constraint that makes the puzzle solvable by pure logic.
Cross sums, Sudoku and the crossword
The three great grid puzzles share a family resemblance. The crossword gives you a grid of crossing words. Sudoku gives you a grid where every region holds 1 to 9 once. Cross sums sits between them: a crossing grid like the crossword, with the distinct-digit discipline of Sudoku, plus arithmetic. If you like the "aha" of a crossword and the rigour of Sudoku, cross sums is the natural next step.
Try it
Whatever you call it, it plays the same. Read the rules, keep the combinations reference nearby, and start a free puzzle.
Frequently asked questions
Are cross sums and Kakuro the same thing?+
Yes. Cross sums is the original English name for the puzzle; Kakuro is the Japanese name that became popular worldwide. The rules are identical: fill runs of white cells with distinct digits that add up to each clue.
Why is it called cross sums?+
Because it works like a crossword where the answers are sums rather than words. Clues give the total for each across and down run, and the runs cross one another, so every cell belongs to one across sum and one down sum.
Is cross sums harder than Sudoku?+
Neither is strictly harder; they exercise different skills. Sudoku is about placement with a fixed digit set per region, while cross sums is about partitioning target totals into distinct digits. People who enjoy mental arithmetic often prefer cross sums.