Polybius Square Cipher

About this calculator

This calculator encrypts or decrypts text with the Polybius square, a classical cipher dating to ancient Greece that arranges the alphabet in a 5×5 grid (I and J typically share a cell) so each letter can be represented by its row and column digits.

Cryptography students and puzzle enthusiasts use it to learn the fundamentals of substitution ciphers and coordinate-based encoding — the same principle later used in more advanced ciphers, like the Polybius-based ADFGVX cipher from World War I. Enter text to encode it into digit pairs, or digit pairs to decode them back to text.