Number Codes

What it's for

Turn letters into the number codes that turn up in puzzles, escape rooms and geocaches, and turn codes back into letters: each letter’s place in the alphabet, the prisoners’ tap code, the digits of an old phone keypad, the five-bit Baudot code of teleprinters, and for numbers, binary-coded decimal and Gray code.

For example, when a clue reads 20-8-5 11-5-25, choose A1Z26 under Back to text and paste it: it says THE KEY.

How to use it

Type text and every code appears at once, each with a Copy button. To decode, choose the code under Back to text (remembered) and paste the coded text.

• A1Z26 numbers the letters from A = 1 (A0Z25 from A = 0), with hyphens between letters and spaces between words.
• The tap code gives each letter as its row and column in a 5 × 5 square, with K tapped as C; decoding takes digit pairs or groups of dots (.. ...).
• Phone keypad multi-tap presses a key once per letter position (44 is H, 0 a space); T9 gives one digit a letter.
• Baudot (ITA2) gives each character five bits, with a shift to figures before digits and punctuation and back to letters after.
• For a number, BCD gives each decimal digit four bits, and Gray code the reflected binary code, where neighbouring numbers differ by one bit.

Example

Type this:

Hello world

A1Z26 is 8-5-12-12-15 23-15-18-12-4, the tap code 23 15 31 31 34 / 52 34 42 31 14, and multi-tap 44 33 555 555 666 0 9 666 777 555 3.

Good to know

T9 can’t be decoded on its own, since one digit stands for three or four letters. Baudot bits are written with the highest bit first (E is 00001); some tables write them the other way round. Letters with accents are coded without them, and characters a code has no symbol for are left out.