What changes on Medium?
Medium Killer puzzles have cages of up to four cells, so the totals get a little bigger. You only get a few starter numbers — most of the puzzle will be solved using cage totals alone. Don’t panic! Just hunt for the smallest cages first.
If Medium feels like a big jump from Easy, that’s normal. Most kids spend a couple of weeks playing Easy puzzles before Medium starts to feel comfortable. If you want a refresher on the basics, the Killer Sudoku page has the full rules with worked examples.
Three new tricks to try
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Locked combos
A two-cell cage with total 4 can only be 1+3 (not 2+2 — no repeats!). Pencil both digits into both cells and watch your row, column and box.
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The 45 rule
Inside any 3×3 box, all the cage totals add up to 45. If five cages add to 38, the missing cell must hold 7.
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Innies and outies
When a cage just barely sticks out of a row, the part outside fills the leftover sum. Tricky — but really powerful.
Mental-maths shortcuts for cage sums
You don’t need to be a maths whiz to play Killer Sudoku, but a few mental-maths tricks make it way faster. The first is "make a 10". When you see a cage like 8+?+? = 13, your brain can jump straight to "I need 5 more from two different digits", which is 1+4 or 2+3.
The second is "subtract from the cage total". Imagine a 3-cell cage totalling 18, and you’ve already placed a 9. The remaining two cells must add to 9, with no repeats and no 9 — so 1+8 (no good, 9 used elsewhere) or 2+7 or 3+6 or 4+5.
The third is the "diff trick" for 2-cell cages. The two digits in a 2-cell cage have to be different and add to the total, so they’re always one number "above and below" the average. A 2-cell cage of 11? Average 5.5, so the digits are 5+6 or 4+7 or 3+8 or 2+9.
When you get stuck
- ✏️ Turn on Notes and pencil in every possible answer
- 🔎 Tap Check — if you have a wrong answer, fix it before going further
- 💡 Tap Hint to fill one cell — it counts in your stats but it’s allowed!
- ↻ Tap Undo to step back if you placed something wrong
Ready for the next step?
When Medium Killer puzzles take you under 12 minutes, give Hard Killer Sudoku a try. Hard puzzles start with no givens at all, and you’ll need every trick from this page plus a few more.
Frequently asked questions
How long should Medium take?
Most kids finish Medium in 12 to 20 minutes. If it takes longer, that’s fine — use Notes and tap Check whenever you want to make sure you’re on track.
Can I switch back to Easy?
Of course — just tap the Easy tab at the top of the board. Your Medium puzzle saves automatically.
Why are there only a few starting numbers?
Killer Sudoku is built around the cages — the totals act like the clues. Medium just gives you a few extra numbers so you have a starting point.
Should I memorise the cage combos?
It really helps. Start with the 2-cell ones (3, 4, 16, 17) — once those are second nature, you’ll spot them in any puzzle.
Try other sudoku games
Different rules, same friendly board. Pick a sibling puzzle to play next.