How is Medium Killer Sudoku different from Easy?

Medium puzzles use larger cages and fewer unique-sum cages, so you can't fill in candidate digits just by recognizing the sum. You'll need to combine the Rule of 45 with classic Sudoku scanning to find your first solid placements.

Do I need to write candidates (pencil marks) at the Medium level?

For most players, yes. Medium Killer Sudoku frequently produces 2- or 3-digit candidate sets per cell, and tracking them mentally becomes unreliable. SudokuPro's built-in pencil-mark feature lets you record candidates and remove them as constraints tighten.

Why does Medium feel harder even though the rules are exactly the same?

The rules don't change between difficulty levels — the cage design does. Medium puzzles include sums that have multiple valid digit combinations, so a single cage no longer locks in its contents on its own. Difficulty in Killer Sudoku is essentially a measure of how many techniques you need to chain together before the first cell is solved.

Medium Killer Sudoku Online: Step Up Your Cage Logic

Medium Killer Sudoku is the intermediate level of the sums-based 9×9 logic puzzle, sitting between the beginner-friendly Easy grids and the demanding Hard boards. The rules are unchanged — fill every row, column, and 3×3 box with the digits 1 to 9, make each dashed cage add up to its target without repeating any digit inside the cage — but cages are larger, sum combinations are no longer always unique, and you'll need to chain two or three techniques together. Medium Killer Sudoku is free to play on SudokuPro, with no registration required.

Characteristics of Medium Killer Sudoku

Medium puzzles are where players stop relying on single-step lookups and start reading the grid as a whole. The 9×9 board and 3×3 regions remain the same, but the cage layout becomes more demanding in three ways.

Larger cages, often 3 to 5 cells, where the same target sum can be reached by multiple digit combinations (a 3-cell cage summing to 10 can be {1,2,7}, {1,3,6}, {1,4,5}, {2,3,5} — none of them automatic).
Fewer "free" 2-cell unique-sum cages at the edges, forcing you to find your first foothold through the Rule of 45 instead of pre-memorized killer pairs.
More cages crossing row, column, and box boundaries, which means cage logic feeds directly into classic Sudoku scanning rather than running parallel to it.

At Medium, the logic shifts from pure placement to combined arithmetic-and-elimination reasoning. A single deduction often produces only a candidate set, not a confirmed digit, so pencil marks become a key tool.

Solving Strategies for Medium Killer Sudoku

Medium boards reward a disciplined sequence of the three foundational techniques. Apply them in this order on every new puzzle:

The Rule of 45 — Look for rows, columns, and 3×3 boxes that are almost fully covered by cages. Add the cage totals; the gap between that total and 45 reveals the missing cell or the missing sum. On Medium puzzles you'll often find that one box has cages totaling, say, 38 plus a single intruding cell — that cell must be 7.
Unique Sum Combinations — Still vital, but used as pencil-mark candidates rather than confirmed digits. Mark every cell of a 3-cell cage summing to 7 with the candidates {1,2,4}, and let row and column constraints narrow the placement.
Cage Elimination — When a cage's candidate set is locked, sweep those digits out of every cell sharing a row, column, or box with the cage. This is where Medium puzzles open up — one cleared cage tends to cascade into two or three more.

Next Steps and Progression

When Medium puzzles start to feel routine, you'll know you're ready for Hard Killer Sudoku, where innies, outies, and overlapping cages take center stage. If a particular cage type is still tripping you up, going back to Easy Killer Sudoku for a quick warm-up is a perfectly valid approach. You can browse all difficulty tiers from the Killer Sudoku main page, review classic-Sudoku fundamentals in the how-to-play guide, or try other variants from the SudokuPro homepage.

FAQ

: Medium puzzles use larger cages and fewer unique-sum cages, so you can't fill in candidate digits just by recognizing the sum. You'll need to combine the Rule of 45 with classic Sudoku scanning to find your first solid placements.
: For most players, yes. Medium Killer Sudoku frequently produces 2- or 3-digit candidate sets per cell, and tracking them mentally becomes unreliable. SudokuPro's built-in pencil-mark feature lets you record candidates and remove them as constraints tighten.
: The rules don't change between difficulty levels — the cage design does. Medium puzzles include sums that have multiple valid digit combinations, so a single cage no longer locks in its contents on its own. Difficulty in Killer Sudoku is essentially a measure of how many techniques you need to chain together before the first cell is solved.