Polybius Square Cipher
Encode letters as row-column pairs in a 5×5 grid.
Output
23 15 31 31 34 52 34 42 31 14
Polybius square (I/J share a cell)
| 1 | 2 | 3 | 4 | 5 | |
|---|---|---|---|---|---|
| 1 | A | B | C | D | E |
| 2 | F | G | H | I/J | K |
| 3 | L | M | N | O | P |
| 4 | Q | R | S | T | U |
| 5 | V | W | X | Y | Z |
Greek historian Polybius (c. 200 BC) used this 5×5 grid for fire-tower signaling. Each letter becomes a row-column pair (A = 11, M = 32). I and J share one cell. Used as a building block in the ADFGVX cipher and many puzzle hunts.
About
The classical Polybius square (c. 200 BC) maps each letter to a row/column pair (A=11, M=32). I and J share a cell. Used as a building block in ADFGVX and as a fire-tower signaling system in ancient Greece.
How to use
- Pick encode or decode.
- Type your text or numbers.
FAQ
Why I and J in the same cell?+
The classical Greek and Latin alphabets had 24/25 letters. To fit in 5x5, two letters share. Tap code (a related cipher used by US POWs in Vietnam) merges C and K instead.