What is Sumplete?
Sumplete is played on a square grid of numbers. Beside every row is a target, and below every column is another. Some of the numbers in the grid are impostors: your task is to delete them so that the numbers you keep in each row add up to that row's target, and the numbers you keep in each column add up to that column's target. Every number is either kept or crossed out — there is no in-between — and both the rows and the columns have to work at the same time.
The name is a blend of "sum" and "delete". It was coined in February 2023 by Daniel Tait, who was experimenting with ChatGPT and asked it to design a new puzzle; the game he built from that conversation spread quickly once people noticed the story behind it. The mechanic itself is older — the mobile game Rullo was built on exactly this rule years earlier — and puzzle books print the same grids under names like Sumdoku or Sum Delete. Whatever it is called, the puzzle is identical, and this page plays it the way the books do: targets on the right and along the bottom.
- Every number in the grid is either kept or deleted.
- The kept numbers in a row must add up to the number on the right of that row.
- The kept numbers in a column must add up to the number below that column.
- Rows and columns share the same numbers, so every decision counts twice.
- Each puzzle on this page has exactly one solution.
How to solve a Sumplete
The single most useful trick is that every line has two sums, not one. The target tells you what the kept numbers add up to; subtracting the target from the line's full total tells you what the deleted numbers add up to. One of those two figures is usually small, and a small figure is easy to reason about. If a row of five numbers totals 33 and its target is 28, you are not looking for numbers that make 28 — you are looking for numbers that make 5, and there are only a couple of ways to do that.
From there the deductions are about size. A number larger than the delete-sum cannot be deleted, so it stays. A number larger than the target cannot be kept, so it goes. If only one number in a line is small enough to fit the delete-sum, that number is the whole delete-sum. Parity helps too: an odd delete-sum needs an odd number of odd numbers crossed out.
Then let the rows and columns talk to each other. Every number you cross out for a row is also crossed out of its column, which changes that column's arithmetic and often forces the next move. Circle the numbers you are sure must stay, cross out the ones that must go, and keep re-reading the lines that have changed. On a well-made board a chain of these small forced moves runs all the way to the end without a single guess.
- Work out each line's delete-sum: full total minus target.
- Reason about whichever of the keep-sum and delete-sum is smaller.
- A number bigger than the delete-sum must stay; bigger than the target must go.
- Once a line's target is met, everything else in that line is deleted.
- Every mark in a row is also a mark in a column — follow the consequences.
Difficulty levels
The 4×4 board uses the digits 1 to 9 and is a warm-up: the lines are short and the forced moves are easy to spot, so it is a good place to learn the delete-sum trick. The 5×5 is the classic Sumplete size — the one that fills most puzzle books — and takes a few minutes of steady deduction. The 6×6 keeps the same small digits but the chains of consequences run longer.
The 8×8 expert board switches to numbers from 1 to 19. Bigger numbers mean more mental arithmetic, but they also mean fewer coincidences: there are simply fewer ways for two different sets of numbers to reach the same total, so the logic is tighter even as the board gets busier.
- 4×4: digits 1–9, a quick warm-up.
- 5×5: digits 1–9, the classic size.
- 6×6: digits 1–9, longer chains of deduction.
- 8×8: numbers 1–19 for confident solvers.
Why play Sumplete online?
Playing on screen removes the bookkeeping. Every row and column shows its target alongside a live total of the numbers still on the board, so you never have to re-add a line after a change. Targets turn green the moment they are satisfied and red if you have deleted too much, a hint reveals one cell when you are stuck, undo is unlimited, and your board is saved locally in your browser so you can come back to it.
Most of all, every puzzle here is generated and then checked by a solver for a single solution. Printed Sumplete grids are occasionally ambiguous — two different sets of deletions that both satisfy every target — which is frustrating when you have solved it correctly and the answer key disagrees. On this page, if all the lines add up, you have found the one and only answer.
- Live totals next to every target.
- Green when a line adds up, red when it can no longer be reached.
- Hint, undo, clear and a full solution when you want it.
- Progress saved in your browser between visits.
- One unique solution per board, checked by a solver.