Number Blocks Solver

Number Blocks Solver — Step by Step

Press 🧱 Blocks and drag across squares to join them into each block of your puzzle. Then press it again and type the given numbers. Press Solve. Or play a generated puzzle and send it here with one click.

Number Blocks Solver: rules, how to use it, tips

Fill each block of n squares with the numbers 1 to n, so that no two touching squares hold the same number.

The rules

The grid is divided into blocks outlined in bold.
A block with n squares contains each number from 1 to n exactly once.
Squares that touch — across a side or at a corner — never hold the same number (in the ‘sides only’ version, corners may touch).
Given numbers can’t be changed.

Using the solver

Choose the size, draw the blocks (or press Sample), then type the given numbers.
Press Solve and step through: block sizes, single squares, the only place left, numbers ruled out by touching, pairs and what-ifs.

Tips

Single squares. A block of one square must be 1, so none of its eight neighbours can be 1.
Two-square blocks. A block of two holds 1 and 2; any square touching both of them can be neither 1 nor 2.
Only place. If a block’s 4 can only fit in one of its squares, put it there.
Touching all of them. When a block’s number must go in one of a few squares, any outside square touching all of those can’t be that number.

The full guide, with a worked example and common mistakes: How to play Number Blocks.

Questions

What does ‘sides only’ mean?

In that version, equal numbers may touch at a corner — only squares sharing a side must differ.

Is there always one answer?

Yes — every puzzle here is checked to have exactly one solution.

How big can the blocks be?

Up to 5 or 6 squares, depending on the option you choose.

How do I solve one from a magazine?

Open the Number Blocks Solver, draw the blocks, type the givens and press Solve.