How to convert a column letter to a number
✓ Verified in LibreOffice 25.8.7.3Turn "AB" into 28 — for driving INDEX, building references, or documentation.
The formula
| App | Formula | Notes |
|---|---|---|
| Excel | =COLUMN(INDIRECT(A2&"1")) | A2 holds the column letters. INDIRECT builds a reference; COLUMN reads its number. |
| Google Sheets | =COLUMN(INDIRECT(A2&"1")) | Identical. |
| LibreOffice Calc | =COLUMN(INDIRECT(A2&"1")) | Identical. |
How it works
INDIRECT turns the text "AB1" into a real cell reference, and COLUMN returns that cell's column number — 28 for column AB. The reverse (number to letter) is the ADDRESS/SUBSTITUTE trick in the convert-a-column-number-to-a-letter recipe. INDIRECT is volatile (recalculates constantly), so for a one-off conversion it's fine, but avoid thousands of them; when you actually need to fetch data by a computed column, INDEX with the numeric result is faster and non-volatile.
Verified, not just documented
We ran =COLUMN(INDIRECT(A2&"1")) in LibreOffice 25.8.7.3 (headless, with forced recalculation) and it returned 28 — exactly the expected result. Every formula here is confirmed by actually executing it.