How to Use the Excel Column Letter to Number Converter

Type a column reference into the box — either letters (like
AA
) or a plain number (like
27
).
Click Convert. The tool detects which direction you meant and runs the conversion instantly in your browser.
Read the result, plus a plain-English sentence confirming exactly what was converted to what.
Nothing you type is uploaded anywhere — this is pure arithmetic running as JavaScript in your browser tab.

How Excel/Sheets Column Numbering Actually Works

Spreadsheet columns are labeled with letters (A, B, C ... Z, AA, AB ...) but internally addressed by a 1-based number (A=1, B=2 ... Z=26, AA=27 ...). This is NOT plain base-26 — it's a bijective base-26 numbering system, and the difference matters. In ordinary base-26 with digits 0-25, there'd be no way to represent "26" without a leading zero-equivalent digit, which doesn't exist in a letter alphabet. Bijective base-26 solves this by treating every digit position as 1-26 (not 0-25), which is exactly why the sequence goes ..., Z (26), AA (27), AB (28), ... instead of skipping straight from Z to a two-letter "A0"-style value that doesn't exist in this system.

The formula this tool implements for letters → number is:

number = 0
for each letter L (left to right):
  number = number * 26 + (position of L in the alphabet, A=1..Z=26)

And for number → letters, the inverse walks the number down using

(n - 1) % 26

and

(n - 1) / 26

— the

-1

at each step is exactly what makes this bijective base-26 instead of ordinary base-26, and it's the detail most hand-rolled implementations get wrong.

Worked Examples

A
→ 1,
Z
→ 26 — the single-letter range.
AA
→ 27 — the first two-letter column, immediately after Z.
AZ
→ 52,
BA
→ 53 — the pattern repeats every 26 columns.
XFD
→ 16384 — the actual rightmost column in every version of Excel since Excel 2007 (the pre-2007 limit was column IV = 256).

Why This Comes Up

This conversion is genuinely useful, not just a curiosity: Excel/Sheets formulas like

INDEX

OFFSET

INDIRECT

, and VBA/Apps Script column addressing frequently need a numeric column index rather than a letter, and vice versa when reading a numeric index back out of a formula result. Anyone scripting spreadsheet generation (via

openpyxl

xlsxwriter

, Google Sheets API, or similar) runs into this exact conversion constantly, since most of those libraries address columns by number internally.

Google Sheets Uses the Same System

Google Sheets uses the identical bijective base-26 column numbering as Excel — column AA is column 27 in both products, and this tool's output is correct for either. The two products diverge on other things (formula names, date serial numbering nuances, week numbering defaults — see this site's other spreadsheet tools) but column letter/number addressing is one area where they match exactly.

Frequently Asked Questions

What's the highest column number Excel actually supports? 16,384 (column XFD), in every version since Excel 2007. Earlier versions (97-2003) capped at column IV (256).

Does Google Sheets have the same column limit? Google Sheets currently allows up to 18,278 columns (column ZZZ) in a single sheet, higher than Excel's XFD cap — though most real spreadsheets never get anywhere close to either limit.

Is my input uploaded or stored anywhere? No. The conversion runs entirely as JavaScript inside your browser tab — nothing is sent to a server, logged, or stored.

Is this tool free? Yes, completely free, no login, no limit.