Excel Column Letter to Number Converter (A1 ⇄ R1C1)
Convert Excel column letters to numbers and back (A=1, AA=27, XFD=16384), split cell references like B12, and convert between A1 and R1C1 notation.
Column letters are bijective base 26: A–Z are 1–26, then AA = 27, AZ = 52, BA = 53, ZZ = 702, AAA = 703.
In R1C1, R[1]C[-1] means one row down and one column left of the cell that holds the formula; R12C2 is the absolute cell B12 ($B$12).
| Input | Read as | Column | Column # | Row | A1 | R1C1 |
|---|---|---|---|---|---|---|
| AA | Column letters | AA | 27 | AA:AA | C27 | |
| XFD | Column letters | XFD | 16384 | XFD:XFD | C16384 | |
| 703 | Column number | AAA | 703 | AAA:AAA | C703 | |
| B12 | Cell (A1) | B | 2 | 12 | B12 | R12C2 · R[9]C[-1] |
| $C$7 | Cell (A1) | C | 3 | 7 | $C$7 | R7C3 |
| R12C2 | R1C1 | B | 2 | 12 | $B$12 | R12C2 |
| R[1]C[-1] | R1C1 (relative to C3) | B | 2 | 4 | B4 | R4C2 |
| A1:C10 | Range | A:C | 1:3 | 1:10 | A1:C10 | R1C1:R10C3 |
Spreadsheet columns are named with letters — A to Z, then AA, AB and so on up to XFD in Excel — while code, APIs and R1C1 formulas use column numbers. This converter turns column letters into numbers and numbers into letters, a whole list at a time, and also understands cell references (B12, $C$7), R1C1 references (R12C2, R[1]C[-1]) and ranges, so you can move between A1 and R1C1 notation.
How to use this tool
- Type or paste values, one per line: column letters, column numbers, cells like B12 or R1C1 references.
- Leave "Detect" on, or say whether plain values are letters or numbers.
- Pick the column limit of your program (Excel, Google Sheets or old .xls).
- For relative R1C1 references, enter the cell that contains the formula.
Formula
number = Σ (letter value) × 26^position, with A = 1 … Z = 26 · letters: repeat n − 1, take n mod 26 as the letter, n ÷ 26
Column names are bijective base 26: there is no zero digit, which is why Z (26) is followed by AA (27) rather than BA. To turn a number into letters, subtract 1 before each division so that 26 maps to Z. Excel 2007 and later have 16,384 columns (XFD) and 1,048,576 rows; .xls files have 256 columns (IV) and 65,536 rows; Google Sheets allows up to 18,278 columns (ZZZ). Values past the chosen limit are reported as errors.
Example
AA = 1 × 26 + 1 = 27. XFD = 24 × 26² + 6 × 26 + 4 = 16,384, the last Excel column. The number 703 = 26² + 26 + 1 becomes AAA. The cell B12 is column 2, row 12, written R12C2 in R1C1 notation, and R[1]C[-1] typed in cell C3 points to B4.
Frequently asked questions
Why is there no column "A0" or zero?
Column letters have no digit for zero, so after Z (26) comes AA (27). That is why simple base-26 conversion gives wrong answers and the formula subtracts 1 at each step.
How do I do this inside Excel?
=COLUMN(INDIRECT("XFD1")) gives 16384, and =SUBSTITUTE(ADDRESS(1,16384,4),"1","") gives XFD. The R1C1 style can be switched on under File → Options → Formulas.
What is the last column in Excel?
XFD, column 16,384, in Excel 2007 and later. Old .xls files stop at IV (256).
Sources
Last updated:
Page address with these inputs: https://kakao.mobile/tools/excel-column-letter-to-number-converter/
Cite or embed this tool
kakaoCalc. (2026, November 8). Excel Column Letter to Number Converter (A1 ⇄ R1C1). https://kakao.mobile/tools/excel-column-letter-to-number-converter/
“Excel Column Letter to Number Converter (A1 ⇄ R1C1).” kakaoCalc, 8 Nov. 2026, kakao.mobile/tools/excel-column-letter-to-number-converter/.
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