How to Solve Cryptarithms — Rules and Examples

Solve cryptarithmetic problems one column at a time. You do not need to guess a complete answer: each arithmetic constraint narrows the possible digits.

A cryptarithm problem, step by step

The sum has three digits. Its hundreds digit comes from a carry, so A = 1.
In the tens column, B plus a carry must make 10. That gives B = 9 and C = 0.
Check the units: 1 + 9 = 10, which writes 0 and carries 1. The complete sum is 1 + 99 = 100.

A = 1, B = 9, C = 0

Digits and letters follow different rules

In Digits mode, each blank is independent and numbers can repeat. In Letters mode, every occurrence of a letter has the same value, and different letters represent different digits.

A multi-digit number cannot begin with zero. Use every visible clue, including known numbers among the letters.

Addition: start with the units

Work from right to left. The digits in a column, plus any incoming carry, must match the result digit. A total of ten or more sends a carry into the next column.

If two possible values fit a column, keep them as pencil notes and use another column to decide between them.

Subtraction: account for borrowing

When the upper digit is smaller, borrow from the next column. That adds ten to the current column and reduces the next upper digit by one. Check both columns together before committing to a value.

Multiplication: check the partial products

Each intermediate row is a product of the top number and one digit of the multiplier. Rows are shifted according to place value. A digit must fit both its partial product and the final sum.

Division: use every step

Each quotient digit determines a product to subtract. The remaining value combines with the next digit of the dividend. All division puzzles on this site finish with zero remainder.

Use the tools without giving up the reasoning

Select a square and type 0–9, or use the number pad. Pencil records possibilities, the eraser clears a value, and undo lets you revise a deduction. Check outlines incorrect entries in red.

Easy uses numbers up to 99. Medium and Hard add more involved deductions; some Hard letter puzzles form words. A solved puzzle stays on screen until you choose the next one.