A1Z26 cipher
Convert letters to numbers with A=1 … Z=26 and back again, with configurable separators, non-letter handling and output case.
Runs in your browserEvery computation happens in your browser — your data never leaves this device.
A = 1, B = 2, … Z = 26
What this tool does
- Turn letters into numbers with A=1 … Z=26 — the classic substitution used in puzzles, CTFs and kids’ cipher games.
- Build numeric sequences from words for IDs, check digits or sort keys, then copy the result instead of counting by hand.
- Decode a string like `8-5-12-12-15` that someone handed you and check whether it really is A1Z26.
- With non-letter characters kept, `hello, world!` becomes `8-5-12-12-15, 23-15-18-12-4!`, so punctuation stays visible in the output.
Example
Input
UniKit
Output
21-14-9-11-9-20
Encoding stores only the letter position, so upper and lower case collapse into the same number — decoding gives back UNIKIT, not UniKit.
Frequently asked questions
What happens if a number is above 26?
You get “Numbers must be between 1 and 26”. The A1Z26 alphabet only has 26 slots, so values like 0, 27 or 99 have no letter and the tool refuses to guess. Seeing one usually means the text is not A1Z26 at all, or the wrong separator is selected.
Why does the decoded text have the wrong capitalisation?
Case is lost during encoding: a and A both map to 1. Decoding outputs uppercase by default, and you can uncheck “Uppercase result” to get lowercase — but the original mixed casing cannot be recovered.
Are punctuation and spaces dropped?
With “Keep non-letter characters” enabled (the default), punctuation and digits survive untouched; whitespace is always ignored and never consumes a number slot. Disable it and every non-letter character is removed from the output.
How is this different from Caesar or Vigenère?
A1Z26 only swaps letters for numbers — no shift, no key, so anyone can reverse it at a glance. Caesar and Vigenère keep letters as letters and need a key. Use A1Z26 for puzzles and numbering, never to protect real data.
Is my input uploaded anywhere?
No. Encoding and decoding run entirely in your browser with JavaScript, the page makes no network requests, and nothing is logged. It works offline too.
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