Spreadsheet Column Converter
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.
- 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.
- What is R1C1 notation for?
- It names a cell by row and column number instead of a letter and a number, and writes relative references as offsets like R[-1]C. A formula in that form reads the same wherever it is copied, which makes it much easier to generate formulas from code or to compare two formulas that sit in different cells.
- Why did my column letters shift after inserting a column?
- A letter is a position, not an identity. Inserting a column renames every column to its right, so a note, macro or piece of documentation that refers to column K afterwards points at different data — silently, because nothing about the reference looks broken. Header names and named ranges survive an insertion; letters do not.
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