Spreadsheet Column Converter
Convert a spreadsheet column letter such as AB or XFD to its number and back, the way Excel and Google Sheets count, and switch cell references between A1 and R1C1 style.
How to Use
- Type a column number (28), column letters (AB), a cell (AB12) or an R1C1 reference (R12C28).
- Read the letters, the number and both reference styles.
- The table says whether the column exists in Excel and Google Sheets, and gives the zero-based index used in code.
- Show Work spells out the base-26 working.
- Click any readout to copy it.
Worked Example
XFD to a number. X is the 24th letter, F the 6th and D the 4th. In base 26: 24 × 26² + 6 × 26 + 4 = 16,224 + 156 + 4 = 16,384, which is 2¹⁴ and the last column Excel allows.
703 to letters. 703 − 1 = 702 = 27 × 26 + 0 → A. 27 − 1 = 26 = 1 × 26 + 0 → A. 1 − 1 = 0 → A. Reading upwards: AAA, the first three-letter column; ZZ, one before it, is 702.
The common mistake: forgetting to subtract 1. Dividing 26 by 26 directly gives remainder 0 and quotient 1, which suggests “A?” with no letter for 0, or the wrong answer BA. Because the letters run from 1 to 26, subtract 1 before each division; then 26 correctly becomes Z.
Show Work
Formulas
A, B, …, Z, AA
VisiCalc, the first spreadsheet, labelled its columns with letters and its rows with numbers in 1979, and Lotus 1-2-3 and Excel kept the convention. Multiplan, Microsoft’s earlier spreadsheet, used R1C1 numbering instead, which Excel still supports as an option.
The letter scheme is a bijective numeration, a positional system with no zero digit, studied by mathematicians long before spreadsheets. It has the nice property that every non-empty string of letters names exactly one column; the price is the extra “subtract 1” in the conversion.
About This Calculator
This converter turns spreadsheet column letters into column numbers and back, converts cell references between A1 and R1C1 style, gives the zero-based index used by programming libraries and says whether the column exists in Excel and Google Sheets. It works for columns of any length.
Everything runs in your browser; nothing is sent anywhere. Dollar signs in absolute references such as $AB$12 are ignored.
Related calculators: Number Base Converter, Arbitrary Base Converter, and Mixed Radix Converter.
Frequently Asked Questions
How do I convert a column letter to a number?
Treat each letter as a digit from A = 1 to Z = 26 and use base 26: multiply the running total by 26 and add the next letter. AB = 1 × 26 + 2 = 28. XFD = 24 × 676 + 6 × 26 + 4 = 16,384, the last column in Excel.
How do I convert a number to column letters?
Subtract 1, divide by 26 and turn the remainder into a letter (0 = A … 25 = Z), then repeat with the quotient. 28 − 1 = 27 = 1 × 26 + 1 → B; 1 − 1 = 0 → A. Reading upwards: AB. The subtraction is needed because there is no zero letter.
Why is this not just base 26?
In ordinary base 26 there would be a zero digit, so after Z (25) would come BA (26), and A would be a leading zero. Spreadsheet columns are bijective base 26: the digits run from 1 to 26, so after Z comes AA, and every string of letters is a different column.
What is R1C1 notation?
A reference style that numbers both rows and columns: R12C28 is row 12, column 28, which is AB12 in the usual A1 style. Excel can switch to it under the formula options, and it is handy for writing formulas with relative offsets such as R[−1]C.
How many columns do spreadsheets have?
Excel since 2007 has 16,384 columns (A to XFD) and 1,048,576 rows. Older Excel stopped at IV (256 columns). Google Sheets allows up to 18,278 columns (ZZZ), within a limit of 10 million cells per spreadsheet.
How do I use the Spreadsheet Column Converter?
Simply type or paste your value and read the result, which refreshes the instant you change something. There is nothing to submit and nothing to wait for.
Do I need to install or sign up for anything?
Not at all — it runs in the browser with nothing to install and no account. After it loads once, it even works without an internet connection.
Is my information private?
Yes. Everything happens in your browser. Nothing you type is sent to a server or saved anywhere.
Common Use Cases
Formulas and scripts
Column AB is 28; in zero-based code it is index 27.
Excel limits
XFD is column 16,384, the last one in Excel.
Two letters
ZZ is 702 and AAA is 703.
Reference styles
AB12 is R12C28 in R1C1 notation.
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