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Polybius Square

Build a five by five or six by six square from a keyword, then turn text into coordinate pairs and back again.

Polybius square encoder

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Square layout
Rows and columns are numbered from one, and in the five by five square the letter J is stored in the cell of the letter I.

How to use the Polybius Square

  1. Type a keyword, which fills the first cells of the square.
  2. Choose the five by five or six by six square and the direction you need.
  3. Paste the text or the coordinate pairs, then copy the converted result.

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Frequently Asked Questions

Common questions about the free online polybius square.

It is a grid of letters where each row and column carries a number, so every letter becomes a pair of coordinates.
The classic square has five rows and five columns, which gives twenty five cells, so one letter pair shares a cell.
The keyword letters are placed first without repeats and the rest of the alphabet follows, which changes every coordinate.
A six by six square holds thirty six cells, which is enough for the twenty six letters plus the ten digits.
Switch to decode, paste pairs of digits separated by spaces, and every pair is read as a row then a column.
Pairs outside the square are skipped and counted, so a mistyped number never silently becomes a wrong letter.
No. It is a substitution cipher over a small alphabet, so it is easy to break and is mainly used for teaching.
No. The square is built and every conversion happens in your browser, with nothing sent to a server.

Last updated: October 10, 2026