Letter to Number Converter
Convert letters to numbers and back using A1Z26, A0Z25, ASCII, hexadecimal, binary or tap (knock) code — a quick decoder for puzzles, ciphers and escape rooms.
Input
Conversion settings
Output
Guides
What this tool does
It swaps letters for numbers, and numbers back into letters, using six different schemes. Puzzle hunters, escape-room designers, geocachers and cryptography students all run into these codes; this converter handles them in one place, in both directions.
The six code types
A1Z26 is the classic: A = 1, B = 2, all the way to Z = 26. It shows up constantly in puzzle boxes and treasure hunts.
A0Z25 is the same idea offset by one, so A = 0. It's the form you want when the puzzle is really about modular arithmetic.
ASCII gives each character its numeric code point — H is 72, the space character is 32, ! is 33. Unlike the alphabet codes, ASCII covers punctuation and digits too.
Hex ASCII and Binary ASCII are the same code points written in base 16 (0x48) and base 2 (0b1001000). Handy when you're staring at a hex dump.
Tap code, also called knock code, lays the alphabet on a grid and encodes each letter as row-then-column: A is 11, H is 23. Prisoners of war famously used it to tap messages through walls.
The traditional tap code uses a 5×5 grid, which only holds 25 letters — K is dropped and written as C. This tool keeps all 26 letters distinct instead, giving K its own code (31) and placing Z at 56, just off the edge of the grid. Encoding and decoding therefore round-trip losslessly, but a purist's 5×5 grid won't decode a 56.
How to use it
Paste your text, pick a code type, choose a direction, and pick how the output should be separated. The result updates as you type.
What happens to spaces and punctuation?
Anything the code can't map passes straight through. In A1Z26, Hi! becomes 8 9 ! — the exclamation mark survives as itself. That's intentional and matches how these puzzles are usually written down, but it does mean word boundaries are preserved as literal spaces in the output.
When decoding, the tool accepts numbers separated by spaces, commas or dashes. Tap code is the exception: it splits on spaces and commas only, because a dash would tear a 11-12 pair in half.
Is my text sent anywhere?
No. The conversion runs entirely in your browser — nothing is uploaded, logged or stored.