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Polybius Square Cipher

Encode letters as row-and-column coordinates using the classic 5x5 Polybius square.

Learn how the Polybius square works

Input

Output

Using This Tool: Guide & Notes Show guide

The Polybius square turns letters into row-and-column coordinates from a 5x5 grid.

How to use it

  • Choose Encode to turn letters into coordinates, or Decode to reverse coordinates into letters.
  • Paste text or coordinate pairs into the input box.
  • Use the square display to check where each letter sits.
  • Copy the output once the coordinate format looks right.

Options and settings

  • The square controls every mapping, so keyword or alphabet changes alter the coordinate output.
  • I/J handling matters because a 5x5 square has only 25 cells.
  • Separators make coordinate pairs readable and easier to decode.
  • Grouping can make long coordinate streams easier to scan.

Notes

  • Polybius is often used as a first stage in stronger classical systems.
  • Coordinates are not secure by themselves; the grid is easy to reconstruct.
See all tools
Tap Code Cipher Send letters as row-and-column tap groups using the classic 5x5 tap code square. Bifid Cipher Mix Polybius square coordinates in fixed-size blocks to create a fractionating classical cipher. Nihilist Cipher Encrypt or decrypt numeric Nihilist ciphertext with a keyed Polybius square and repeated additive key. ADFGX Cipher Use a keyed ADFGX square followed by keyed columnar transposition.
Related Article

Polybius Square Cipher: Turning Letters into Coordinates

How a 5×5 grid turned the alphabet into numbers, signals, and one of classical cryptography's most useful building blocks.

Read the article
Signal acquired

A note from the team

We build these tools because we love cryptography, encoding, and making difficult ideas easier to explore. If they've helped you, even a small coffee means the world to the project. Thank you!

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