Letters to numbers (A1Z26)

The A1Z26 cipher

Every letter becomes its position in the alphabet: A is 1, B is 2, and so on to Z at 26. TREASURE MAP becomes 20-18-5-1-19-21-18-5 13-1-16. It's barely a cipher, since there's no key, but it's one of the most common layers in puzzle hunts, escape rooms and kids' activity books. The numbers look like data and don't look like words.

Reading numbers back

The trouble with A1Z26 is the gaps. 1225 could be A B B E, L B E, A V E or L Y, so the decoder needs some separation to work with. It reads:

• Hyphens, commas or dots between letters, with spaces or / between words: 8-5-12-12-15 23-15-18-12-4.
• Spaces between letters, with / between words: 8 5 12 12 15 / 23 15 18 12 4.

Any number outside 1–26 shows as ?. Several of those in a row usually means the numbers aren't letter positions at all. They might be ASCII codes (where 65 is A), page-line-word references to a book, or a Polybius square.

Variations to try

• A = 0. Programmers count from zero, so some puzzles do too. Switch the numbering above.
• Reversed (A = 26, Z = 1). Decode normally, then run the result through Atbash.
• Shifted. If the numbers decode to gibberish of the right length, the letters may have been Caesar-shifted first. Paste the result into the Caesar tool and check the brute-force table.