Encode and decode text with the Polybius square, mapping letters to row and column digits. Runs entirely in your browser.
The Polybius square, devised by the ancient Greek historian Polybius, places the alphabet in a 5x5 grid and represents each letter by its row and column numbers. It underpins later ciphers like the tap code and Nihilist cipher. This tool converts text to coordinate pairs and back.
Input:
HELLO
Output:
23 15 31 31 34
Why do I and J map to the same pair?
A 5x5 grid has 25 cells for 26 letters, so I and J share one. Decoding shows I for that cell.
What do the two digits mean?
The first digit is the row and the second is the column in the 5x5 square, both numbered 1 to 5.
Is it secure?
No. It is a fixed encoding with no key, useful for puzzles, tap code and as a building block.
Does my text leave the browser?
No. It runs locally in your browser.
Encode and decode text with the Polybius square, mapping each letter to row/column digit pairs (5x5, I/J shared). Runs entirely in your browser.
Supported Tools: