Cross sums: fill the white squares with 1 to 9 so each run adds up to its clue, with no digit repeated in a run
Kakuro, also called cross sums, is a crossword made of numbers. The grid has black squares and white squares. A black square can hold one or two clues split by a diagonal: the number above the diagonal is the total of the run of white squares to its right, and the number below is the total of the run beneath it. You fill every white square with a digit from 1 to 9 so that each run adds up to its clue and no digit repeats inside a run. Every grid here is new, comes in three sizes, and has exactly one solution, which a solver confirms before the puzzle appears.
Choose a grid: 6×6 is easy, 8×8 is medium and 10×10 is hard. The sizes count the clue row and column.
Press New puzzle. Black squares hold the clues; white squares are for your digits.
Tap a white square, then a number on the pad. Clear removes a digit.
The helper under the grid shows the selected square's across and down runs and every set of different digits that can make each total.
On a keyboard, arrow keys move between white squares, skipping the black ones; type 1 to 9, Backspace clears, Ctrl+Z undoes.
With Show clashes on, a repeated digit in a run turns red, and so does a run that goes over its total or finishes on the wrong one.
Fill every white square correctly and the puzzle ends, with your time saved as a best for that size.
Number sense and deduction across two directions at once. Each white square sits in one across run and one down run, so the digit has to fit two sums and two no-repeat rules together. Solving means knowing, or working out, which sets of different digits make a total in a given number of squares, and then crossing those sets with the ones from the other direction. It exercises quick addition, the partitioning of numbers into distinct parts, and keeping several candidates in mind until a crossing run settles them.
Start with runs that have only one possible set of digits: 3 in two squares is 1+2, 4 in two is 1+3, 16 in two is 7+9, 17 in two is 8+9, 6 in three is 1+2+3, 7 in three is 1+2+4, 23 in three is 6+8+9 and 24 in three is 7+8+9.
Where an across run and a down run share a square, the digit must be in both runs' possible sets. Often only one digit is common to both.
Big and small totals are the easiest: they force the high or low digits. Totals near the middle of their range have many sets and are best left for later.
Once one digit in a two-square run is known, the other is the total minus that digit.
Use the helper under the grid to see every digit set for the runs through the selected square.
If a run's total leaves only one digit missing, subtract what is already there.
Kakuro is a number-logic puzzle laid out like a crossword. Instead of words you write digits from 1 to 9 in the white squares. Each across or down run of white squares must add up to the clue in the black square before it, and the digits in a run must all be different.
A black square may be split by a diagonal. The number in its top-right part is the total of the run to the right of it. The number in its bottom-left part is the total of the run below it. A black square with no number starts no run.
No. Within one across run or one down run every digit is different. The same digit may appear again in a different run, including a run in the same row that is separated by a black square.
Yes. After our generator fills a layout with random digits and reads the totals off, a solver looks for a second filling. If it finds one, the generator changes a digit where the two fillings differ, which changes the totals, and checks again. A puzzle is shown only when the solver proves the filling is unique.
Because the clues are sums and the runs cross each other like the words in a crossword. The two names describe the same puzzle.
6×6 (easy), 8×8 (medium) and 10×10 (hard). The size includes the clue row along the top and the clue column down the left, so a 6×6 grid has a 5×5 playing area. Each size keeps its own best time.
It is free with no sign-up. Your best time for each size, your number of solved puzzles and the Show clashes setting are saved in this browser only.