Sudoku LunaSudoku Luna
BeginnerBasics

Last Digit

When eight copies of a digit are already on the board, the ninth position is forced.

What it is

Each digit appears exactly nine times in a finished grid. Once you have placed eight of them, the ninth has only one legal home left: the single cell not blocked by an existing copy. It is the same counting idea as the full house, but tracked per digit across the whole board rather than per unit.

How to spot it

Count how often a digit appears. At eight, look at the three boxes, rows or columns still missing it — usually only one cell survives the crossing lines. Puzzles often place eight copies of a digit early, so it is worth a quick count of your most frequent digits.

Worked example

Step through the reasoning below. Each step adds one layer: first the position, then the pattern, then the candidates involved, and finally what can be eliminated.

Step 1 of 3: The starting position

Pattern cells
6/2
Digits
Eliminations

Press a marked square to point it out on the board above.

Why it matters

Tracking digit counts gives you a cheap second way to find placements when cell-by-cell scanning stalls. It is also how experienced solvers notice that a digit is nearly complete and worth attacking.

Practise now

Solve a puzzle where this technique decides the game

Practise now

Frequently asked questions

How is this different from a hidden single?

A hidden single looks at one unit. The last digit looks at the whole board and uses the fact that a digit appears exactly nine times. In practice the final placement often qualifies as both.

Is it worth counting digits deliberately?

On harder puzzles, yes. Digits with seven or eight placements are the most constrained on the board and are usually where the next breakthrough hides.

Put it to use

Where you will meet it

This pattern is the backbone of easy grids. Start one and you will use it within a few moves.

Play Easy

Stuck on a grid of your own?

Type the position into the solver and it walks the whole solution, naming the technique behind every step — including this one.

Open the solver

Prefer paper? Ready-made Easy sets as a PDF.Print puzzles

Finished reading? Mark it done and the learning path remembers where you got to.

Related techniques