Sumplete vs Killer Sudoku: Delete Down or Fill Up?

Sumplete and Killer Sudoku both revolve around target sums, but they run in opposite directions. Sumplete starts with a full grid and you delete numbers until each row and column hits its target. Killer Sudoku starts empty and you fill digits up to each cage’s total. Same arithmetic instinct, completely different solving flow.

Sumplete vs Killer Sudoku: The Quick Answer

Both puzzles center on target sums, so the confusion makes sense — but once you see them side by side, the split is clean.

Feature	Sumplete	Killer Sudoku
Starting grid	Full (numbers already placed)	Empty (blank 9×9)
Your move	Delete numbers	Fill in digits
Goal	Each row & column’s remaining sum = edge target	Rows, columns & 3×3 boxes each hold 1–9 once; each cage sums to its target
Repeat numbers	Allowed	Forbidden inside each cage
Constraint type	Sum targets only	Placement rules + sum targets
Grid size	Variable (5×5 to start)	Fixed 9×9
Origin	AI-created, Daniel Tait, 2023	Classic Sudoku variant
Arithmetic load	Basic addition + elimination	Addition + Sudoku deduction

The sections below unpack each row — including the question that always comes up: which one is actually easier to start with?

What Is Sumplete?

Sumplete was created in 2023 by Daniel Tait, who used ChatGPT to generate the puzzle concept. According to the official game site, the AI “not only came up with the idea, but also coded the game, designed it, and even named it.” Tait launched it at sumplete.com, and it spread quickly through puzzle communities.

The mechanic is the reverse of what most number puzzles do. You start with a grid that is already full of numbers — nothing is blank. Your only action is to cross numbers out. When you’re finished, the numbers still standing in each row must add up to the target shown on that row’s right edge. The numbers still standing in each column must add up to the target shown at the column’s bottom.

A few things that surprise first-time players:

No placement rule. Numbers can repeat freely within a row or column. There’s no Sudoku-style uniqueness constraint — a row might contain two 4s, and that’s completely fine.
No guessing. Every Sumplete puzzle is designed to have a logical path from start to finish. You always have enough information to work out what to cross out next.
Flexible grid size. The game starts at 5×5, which is approachable, and scales up through 7×7 and beyond.

For a full walkthrough of how the deletion logic works, see our guide to how Sumplete is played.

What Is Killer Sudoku?

Killer Sudoku is a variant of classic 9×9 Sudoku. The grid starts completely empty, and your job is to fill it so that:

Each row holds the digits 1–9 exactly once.
Each column holds the digits 1–9 exactly once.
Each 3×3 box holds the digits 1–9 exactly once.
Each dotted-line cage sums to its printed target — and no digit may repeat within a cage.

That fourth rule is the addition on top of standard Sudoku. The no-repeat-in-cage constraint is absolute: even if two cells in the same cage sit in different rows and columns, they cannot hold the same digit.

One of the most powerful solving techniques is the 45 rule: because every row, column, and 3×3 box contains exactly the digits 1 through 9, each one always sums to 45. When you can see all but one cage that overlaps a particular row or box, you can calculate what that remaining cage’s cells must total — even before knowing which specific digits go where.

Our how to play Killer Sudoku guide walks through the 45 rule, cage combinations, and the rest of the core techniques step by step.

The Core Difference: Delete vs Fill

This is the hinge the whole comparison turns on.

In Sumplete, you look at numbers already on the board and decide which ones to remove. You are working downward — pruning away what doesn’t belong until the numbers that remain add up correctly. The mental motion is consistent throughout: scan a row or column, find what’s pushing the sum over target, and eliminate it.

In Killer Sudoku, every cell is an open question. You work upward — building the grid from nothing by deducing which digit belongs in each empty cell. You hold three constraint layers simultaneously: the row, the column, the 3×3 box — and then the cage sum on top of all three.

That direction flip changes your entire solving strategy. In Sumplete, your first move is to find something you can cross out. In Killer Sudoku, your first move is to find somewhere you can place a digit.

Same arithmetic instinct, opposite direction — Sumplete deletes down, Killer Sudoku fills up.

One more contrast worth flagging: because Sumplete has no placement uniqueness rule, repeated numbers are completely valid. A row might contain three 4s — what matters is only that the survivors sum to the target. Killer Sudoku’s structure is far tighter. Every constraint (row, column, box, cage) removes candidates from every other cell. The two puzzles use the same arithmetic surface, but the underlying logic is very different.

Which Is Easier?

This is a “different kind of effort” question more than a clean difficulty ranking.

Sumplete is faster to learn. The rules fit in two sentences. The 5×5 starter grid is small enough to hold in your head, and your first move is usually obvious — look for a row or column where one number would push the sum over the target and cross it out. That first click is satisfying, and it teaches you how the whole puzzle works.

Killer Sudoku has a steeper first session. You need to hold three Sudoku constraint layers in your head before you can make a meaningful move, then add the cage rules on top. A blank 9×9 grid can feel like there’s nowhere to start. The turning point is when you internalize the 45 rule and learn the most common cage combinations: a two-cell cage summing to 3 can only be {1, 2}; a two-cell cage summing to 17 can only be {8, 9}. Once those patterns are automatic, the puzzle opens up quickly.

Sumplete tends to feel lighter and quicker to get going. Killer Sudoku tends to feel like a longer, more layered session. Neither is objectively harder — they exercise different instincts. Which feels harder depends on what you already find intuitive. If arithmetic comparison clicks for you naturally, Sumplete may feel too easy once you’ve done a few. If constraint logic is your thing, Killer Sudoku may feel more engaging from the start.

Which Should You Try First?

If you’re new to both: start with Sumplete. The single-rule structure, the 5×5 entry grid, and the immediate satisfaction of watching a row total lock in make it genuinely beginner-friendly. The learning curve is measured in minutes, not sessions.

If you already play Sudoku: Killer Sudoku is the natural next step. You already think in rows, columns, and boxes — the cage sum layer adds a new constraint rather than replacing the whole framework. Our how to play Killer Sudoku guide walks through the cage logic and gets you solving quickly.

Once you’re comfortable with Killer Sudoku basics, our Killer Sudoku combinations chart is worth bookmarking. It lists every valid digit set for every cage sum and cage size, so you stop hunting through candidate pairs by hand and start eliminating with confidence.

And if you want to see how Killer Sudoku compares to the other major cage puzzle, our KenKen vs Killer Sudoku guide covers those differences in the same format.

Try the Sumplete Approach Right Now

Reading about a delete-down puzzle and actually playing one are two different things. The fastest way to get a feel for the Sumplete mechanic — a full grid, crossing out numbers, watching row and column totals click into place — is to play a round right now.

Clear Sum is our free, browser-based puzzle game built on the same deletion mechanic as Sumplete. Click numbers to cross them out, aim to match each row and column target, and work toward the clean solve. No download. No sign-up. Just the delete-down logic, ready to go in your browser.

∑ Clear Sum — free number puzzle Click numbers to delete them and hit every row and column target — the same delete-down logic as Sumplete. About a minute to learn, free in your browser, nothing to install. Try Clear Sum ↓

Give it a few rounds before you sit down with a full Sumplete or Killer Sudoku grid. The deletion instinct becomes second nature faster than you’d expect.

Frequently Asked Questions

Are Sumplete and Killer Sudoku the same puzzle?

No — though both involve target sums, the mechanics run in opposite directions. Sumplete gives you a full grid and asks you to cross out numbers until each row and column hits its edge target; there are no placement rules and numbers can repeat freely. Killer Sudoku gives you an empty 9×9 grid and asks you to fill it so every row, column, and 3×3 box holds 1–9 exactly once, with each cage also summing to a printed target and cage repeats strictly forbidden. The two puzzles share arithmetic intuition but little else about how they work.

Is Sumplete easier than Killer Sudoku?

For most beginners, Sumplete is the quicker start — the rules are simpler and the 5×5 entry grid is forgiving. Killer Sudoku requires holding the Sudoku placement structure in your head before you can make a confident first move, which takes longer to learn. That said, experienced Sudoku players sometimes find Killer Sudoku more intuitive because it builds on skills they already have. Difficulty depends on your background; what’s consistent is that Sumplete has the shorter on-ramp.

Do you need to be good at math for Sumplete or Killer Sudoku?

No — basic addition is all either puzzle needs. Sumplete asks whether the remaining numbers in a row add up to the edge target; Killer Sudoku asks whether a cage’s digits hit their sum. The real skill in both puzzles is logical elimination, not arithmetic speed. If you’re comfortable adding single-digit numbers, you have all the math either game requires.

Which should a beginner try first, Sumplete or Killer Sudoku?

Sumplete. The rules take about a minute to learn, the 5×5 grid is small enough to see the whole puzzle at once, and the first move is almost always obvious. Killer Sudoku works better as a second step — ideally after you’re comfortable with standard Sudoku and can think naturally in rows, columns, and 3×3 boxes. Start with Sumplete, play a few rounds of Clear Sum to build the deletion instinct, then try a Killer Sudoku beginner grid when you’re ready for more layers.

Sources: Sumplete — sumplete.com (creator Daniel Tait, AI-created 2023, delete mechanic, row/column targets) · Wikipedia — Killer Sudoku (cage no-repeat rule, 45 rule, fixed 9×9 structure)

About the author: Jay M. spent years working in education — first at a private tutoring company, then running a coding academy branch — before moving into educational content creation. The guides and puzzles on Make10s come from a long-standing interest in how everyday number skills stay useful and enjoyable throughout adult life. Just for fun — not medical advice.