Because there's no zero digit. The pattern is A=1, …, Z=26, AA=27, AB=28, …, AZ=52, BA=53, etc. That's bijective base-26 — every positive integer has a unique letter representation and vice versa.

Does Excel really have a column limit?

Yes: 16384 columns (XFD) in modern Excel. Google Sheets caps at 18278 columns (ZZZ). Both are well above what this tool can produce.

Spreadsheet Column Converter

Convert

Excel and Google Sheets use bijective base-26 to name columns: A through Z, then AA, AB, …, AZ, BA, …, ZZ, AAA, etc. That's not quite base-26 (there's no zero digit), so the conversion is just slightly off from naive arithmetic. This tool handles both directions, with a 1-based default that matches what you see in the app and an optional 0-based mode for code.

—

ValueRow

0-based numbers (for code / APIs)

LetterAB
Number28
A1 cellAB1
R1C1 cellR1C28

1-based by default — matches what you see in Excel / Sheets. Toggle 0-based for indexing APIs.

How to use

Pick the direction — letter → number or number → letter.
Type your value. The other notations update live, including the full A1 (`AB12`) and R1C1 (`R12C28`) cell references.
Switch to 0-based if you're talking to an API that indexes columns from 0.

Frequently asked questions

Why isn't AA = 26?: Because there's no zero digit. The pattern is A=1, …, Z=26, AA=27, AB=28, …, AZ=52, BA=53, etc. That's bijective base-26 — every positive integer has a unique letter representation and vice versa.
Does Excel really have a column limit?: Yes: 16384 columns (XFD) in modern Excel. Google Sheets caps at 18278 columns (ZZZ). Both are well above what this tool can produce.