What Is the A1Z26 Cipher? A Simple Explanation

The A1Z26 cipher is one of the oldest and simplest substitution ciphers in cryptography. It replaces every letter of a message with a number based on its position in the alphabet — A becomes 1, B becomes 2, and so on through Z, which becomes 26.

Why it’s called A1Z26

The name describes its two endpoints: A=1 and Z=26. Unlike more complex ciphers, A1Z26 doesn’t require a secret key — the rule is always the same, which makes it ideal for anyone learning to convert letters to numbers for the first time.

How encoding works

Replace every letter with its alphabet position and separate the numbers with a hyphen. The word CIPHER becomes 3-9-16-8-5-18. Spaces between words are usually preserved so multi-word phrases stay readable — see more worked examples.

How decoding works

Decoding reverses the process: split the numbers apart, then match each one back to its letter using the same A=1 through Z=26 rule. Because there’s no hidden key, decoding is just as fast as encoding.

A1Z26 vs other letter-number systems

A1Z26 isn’t the only way to map letters to numbers. Some systems start counting from zero instead of one — see our A1Z26 vs A0Z25 comparison. Others use raw ASCII character codes instead of alphabet position entirely.

Where you’ll see A1Z26 used

• Classroom cryptography lessons introducing basic code-breaking
• Escape room and treasure hunt puzzles
• Casual numerology explorations of names and words
• Simple secret messages between friends

Ready to try it? Use the free converter to encode any message instantly, or check the complete alphabet chart.