Excel column letter ↔ number — A→1 / 27→AA / 16384→XFD
Convert spreadsheet column letters (A, B, ..., Z, AA, AB, ..., AZ, BA, ..., XFD) and column numbers (1, 2, ..., 16384) in both directions. Process many entries at once — one per line. Use the Mode toggle to switch between letter → number and number → letter. Handy when working with VBA, Apps Script, openpyxl, or SheetJS where you need to map a column index to its bijective base-26 letter form. Runs entirely in your browser.
How to use
Paste one entry per line, pick a direction (letter → number or number → letter) and click Convert. The conversion uses spreadsheet-style bijective base-26 (1-indexed) — the same scheme Excel, Google Sheets, and Numbers use. Mixed case and leading/trailing whitespace are fine; empty lines are skipped, and invalid entries are emitted as `?` so the line correspondence stays aligned. Copy the result or save as .txt with one click.
FAQ
- Is my input uploaded?
- No. Everything runs in your browser as pure string math — no external API calls.
- What happens past Excel's XFD (16384) limit?
- We do not enforce an upper bound. XFD = 16384 is the Excel 2007+ limit, but Google Sheets can go higher, so the tool keeps converting as long as the input is a positive integer.
- Does case or whitespace matter for column letters?
- No. `aa` is treated as `AA` (= 27), and ` Z ` becomes 26. Anything containing non A–Z characters (e.g. `A1`, `列A`, `A B`) is rejected and that line is emitted as `?`.
- What about 0, negative numbers, or decimals?
- Excel column numbers are positive integers, so 0, negatives, and decimals are rejected (emitted as `?`). Leading zeros are allowed and treated as the underlying integer (e.g. `007` → G).
- Why is this 'bijective base-26' rather than regular base-26?
- In ordinary base-26, `AA` would be 0 — Excel needs each digit in the 1–26 range so it can start at A = 1 with no zero digit. The wraparound from Z (26) to AA (27) is unique to this bijective numeral system.
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