The A1Z26 cipher turns letters into numbers by their place in the alphabet: A=1, B=2, C=3, … Z=26. To encode, replace each letter with its number; to decode, turn each number back into its letter. For example HELLO becomes 8-5-12-12-15. You can convert either direction instantly with the A1Z26 cipher tool, but the one thing that trips people up is the separators between numbers — which is where most of this guide focuses.
TL;DR
- Each letter maps to its alphabet position: A=1 … Z=26.
- HELLO =
8-5-12-12-15. - Separators are essential:
1215is ambiguous — it could be LO (12-15) or ABAE (1-2-1-5). - It is a substitution code for puzzles and learning, not real encryption — it is trivial to break.
- Common variants: reverse (Z=1), 0-indexed (A=0), and a slash between words.
The Full A1Z26 Table
The whole cipher is just this one-to-one map between the 26 letters and the numbers 1–26.
| Letter | Number | Letter | Number |
|---|---|---|---|
| A | 1 | N | 14 |
| B | 2 | O | 15 |
| C | 3 | P | 16 |
| D | 4 | Q | 17 |
| E | 5 | R | 18 |
| F | 6 | S | 19 |
| G | 7 | T | 20 |
| H | 8 | U | 21 |
| I | 9 | V | 22 |
| J | 10 | W | 23 |
| K | 11 | X | 24 |
| L | 12 | Y | 25 |
| M | 13 | Z | 26 |
How to Encode (Letters to Numbers)
Take each letter, find its position, and write the numbers with a separator between them. Spaces between words are usually shown with a slash (/).
| Letter | Position |
|---|---|
| H | 8 |
| E | 5 |
| L | 12 |
| L | 12 |
| O | 15 |
So HELLO = 8-5-12-12-15, and CAB = 3-1-2. A two-word phrase such as HI THERE is 8-9 / 20-8-5-18-5.
How to Decode (Numbers to Letters)
Reverse the process: read each number and swap in the matching letter. Given 19-15-19, that is 19=S, 15=O, 19=S — SOS. Given 26-5-2-18-1, that is ZEBRA. As long as the numbers are separated, decoding is unambiguous.
Why Separators Matter More Than Anything
This is the part that breaks real messages. If you drop the separators, the digits become ambiguous because numbers 1–9 are one digit and 10–26 are two. Take 1215 with no separators:
| Reading | Result |
|---|---|
| 12-15 | LO |
| 1-2-1-5 | ABAE |
| 12-1-5 | LAE |
| 1-2-15 | ABO |
All four are valid ways to split the same digits, and only the sender knows which was intended. That is why A1Z26 is almost always written with hyphens, spaces, or commas between numbers — the separator carries as much information as the digits do. If you are ever handed a run of digits with no separators, you may have to try several splits, which is exactly what makes an unseparated A1Z26 mildly puzzle-like rather than a clean code.
Common Variants
- Reverse (Z1A26). The alphabet is numbered backwards, so A=26, B=25, … Z=1. It is A1Z26 run through an Atbash-style flip of the numbering.
- Zero-indexed (A=0). Some computing contexts use A=0 … Z=25 instead of 1–26. Always confirm which base a puzzle uses.
- Word separators. A slash (
/) or a double space commonly marks the gap between words so the decoded text keeps its spacing.
Is A1Z26 Secure?
No. A1Z26 is a fixed substitution that anyone can reverse in seconds with the table above — there is no key and no secret. It is popular in escape rooms, ARGs, puzzle hunts, and classrooms because it is easy to learn and fun to spot, not because it hides anything. For messages that actually need to stay private, use modern encryption rather than a letter-to-number code. If you enjoy this style of puzzle, the Caesar cipher and Atbash cipher are the natural next steps.
FAQ
What is the A1Z26 cipher?
A simple substitution that replaces each letter with its position in the alphabet: A=1, B=2, up to Z=26. HELLO becomes 8-5-12-12-15.
How do you decode A1Z26?
Turn each number back into the letter at that alphabet position. For example 3-1-2 is C-A-B = CAB. Separators between the numbers make the reading unambiguous.
Why does 1215 have more than one answer?
Without separators the digits can be split in several valid ways: 12-15 is LO, but 1-2-1-5 is ABAE and 12-1-5 is LAE. Only a separator tells you which split was intended.
Is the A1Z26 cipher secure?
No. It has no key and is reversed instantly with the alphabet table, so it is for puzzles and learning, not for protecting real messages.
What is the reverse of A1Z26?
The Z1A26 variant numbers the alphabet backwards (A=26 … Z=1). It is the same idea with the numbering flipped, similar in spirit to the Atbash cipher.
A1Z26 is the first cipher most people ever meet, and it teaches the real lesson early: the code is only half the message — the separators, the direction, and the base are the other half.
Convert letters to numbers and back with the A1Z26 cipher tool, translate dots and dashes with the Morse code alphabet chart, or decode raw bytes in the binary to text guide. Browse every converter in the tools list.