A1Z26 vs A0Z25: What’s the Difference?

A1Z26 and A0Z25 are close cousins — both map letters to numbers in alphabetical order — but they start counting from a different point, which changes every single value in the sequence.

A1Z26: counting from one

In A1Z26, A equals 1 and counting continues normally through Z, which equals 26. This matches how most people naturally count a letter’s position in the alphabet.

A0Z25: counting from zero

A0Z25 shifts everything down by one, so A equals 0 and Z equals 25. This mirrors how many programming languages index arrays starting at zero, which is why developers sometimes prefer it.

Side-by-side comparison

Word	A1Z26	A0Z25
BAD	2-1-4	1-0-3
CAT	3-1-20	2-0-19
HELLO	8-5-12-12-15	7-4-11-11-14

Every value in A0Z25 is exactly one less than its A1Z26 counterpart. See more side-by-side examples across different words.

When to use each one

Use A1Z26 for general puzzles, classroom lessons, and anything meant to feel intuitive. Use A0Z25 when working alongside code that indexes from zero, or when you want a puzzle variant that trips up solvers expecting the standard mapping.

You can switch between both modes — plus reverse alphabet and ASCII — any time in the main converter, or browse the full alphabet chart.