Killer Sudoku Medium – Play Free Online
Building a puzzle with a single solution…
Killer learning studio
Turn cage totals into proven moves
Killer Sudoku becomes clear when every cage is read together with the row, column and box around it. Start with the information that is forced, keep combinations visible, then let a complete unit prove the next step.
01
Three signals, one proof
- 1A cage total tells you which digit combinations can exist.
- 2No digit may repeat inside a cage, so the combination remains precise.
- 3Rows, columns and boxes still total 45, linking local cages to the whole grid.
02
A cage total becomes a safe digit
A two-cell cage totalling 3 has only the digits 1 and 2. When the row already contains 1, the open cage cell is proven to be 2 — no guess is involved.
- 1Read the cage total and its number of cells.
- 2Remove combinations that repeat a digit or conflict with the grid.
- 3Place only the remaining digit the evidence allows.
03
Four levels, one connected method
Each difficulty strengthens one Killer skill. Pick the level that matches your current evidence, then move on when the next technique feels explainable rather than merely familiar.
Easy
- Best for
- Your first cages and calm, verifiable openings.
- Practice focus
- Extreme two- and three-cell combinations.
- Ready to progress when
- You can use cage digits with row and box constraints.
Medium
- Best for
- Solvers comfortable with basic cage combinations.
- Practice focus
- The Rule of 45 across one row, column or box.
- Ready to progress when
- A missing total becomes a useful candidate restriction.
Hard
- Best for
- Players keeping clean candidate combinations.
- Practice focus
- Innies and outies across a useful boundary.
- Ready to progress when
- You can explain an inside or outside remainder.
Expert
- Best for
- Experienced solvers who combine several constraints.
- Practice focus
- Multi-unit totals of 90 and 135.
- Ready to progress when
- You can choose a region with a provable multi-unit remainder.
04
Continue with real Killer tools
Read the underlying method, practise its exact technique, verify a position in the solver or print a fresh Killer grid — each route keeps the same cage-first logic intact.
Killer Sudoku medium
Connect cage totals with the 45 rule
Medium Killer Sudoku asks you to connect information instead of waiting for every cage to become forced. Wider cages and fewer extreme sums make complete rows, columns and boxes your next dependable source of deductions.
First safe move
Choose a row, column or box whose cage totals leave one small remainder against 45. Treat that remainder as a constraint, not a guess.
A balanced medium-level routine
- 01
Resolve any remaining forced cage combinations before carrying sums across a region.
- 02
Add the cage totals inside one nearly complete row, column or box and compare them with 45.
- 03
Use the missing total together with candidates and cage boundaries; do not place a digit from the total alone.
Medium
Next technique: the Rule of 45
Every full unit totals 45. Once known cages account for most of that unit, the remaining sum becomes a precise constraint for its open cells.
Learn Rule of 45Learn Killer Sudoku step by step
Start with cage combinations, then build toward the Rule of 45, innies and outies, and precise cage exclusions.
Medium Killer Sudoku: common questions
Why do medium Killer grids feel less obvious?
They use wider cages and fewer extreme totals, so a cage may have several valid combinations. Progress comes from linking that cage with a row, column or box instead of treating it alone.
When does the Rule of 45 become useful?
Use it when a complete row, column or box is mostly covered by known cage totals. Because digits 1 to 9 total 45, subtracting the known totals gives the exact sum left in the uncovered cells.
Explore Rule of 45Does a missing total tell me the exact digit immediately?
Only when one cell is left or the remaining candidates permit one combination. Otherwise the total is a constraint: combine it with no-repeat, cage shape and the row, column or box.
Should I keep candidate notes at this level?
Yes. Notes prevent you from treating an open cage as fixed too early and make the combination that fits a 45-total easier to verify.
What is the best next lesson after medium Killer Sudoku?
The Rule of 45 is the natural next lesson. It turns local cage arithmetic into a reusable whole-unit deduction.