Use the free Spreadsheet Column Letter Converter below: your data never leaves your browser — all work happens on your device, and nothing is uploaded to any server.
Spreadsheets name their columns with letters, not numbers. The first column is A, the second is B, and after Z comes AA, then AB, and so on. That system is simple for the first 26 columns, but it quickly becomes confusing. Is column 137 called EA or something else? The Spreadsheet Column Letter Converter answers that question in one click: type a number and get the letter, or type a letter and get the number back.
The conversion is not ordinary base-26 maths, and that is why people get it wrong. In normal base 26, there would be a zero digit, but spreadsheet columns have no zero. A is 1, not 0, so the counting rolls over in a special way. Column 26 is Z, column 27 is AA, column 52 is AZ, and column 53 is BA. Guessing from the pattern usually fails at exactly those rollover points, and a wrong letter in a formula points at the wrong data without any warning.
To use the tool, type a column number into the first box and press To letters. Type letters into the second box and press To number. The tool also lists a whole range at once: set how far to count, press Show list, and you get every number with its letter, from 1 = A up to the limit you chose. That list is handy when you are building a wide sheet and want to check a whole block of columns in one look.
The most common use is writing formulas. A formula that references column AA by mistake when it should reference AB will silently pull the wrong values, and the error may only surface weeks later. Checking the letter first takes two seconds and removes that whole class of mistake. Teachers preparing grade sheets, shop owners building stock lists, and anyone who works with exported data all run into wide sheets sooner or later.
The reverse direction matters just as much. Error messages and documentation often name a column by its letter, such as ‘check column DZ’. If you need to count to that column in code or in a script, you need its number, and counting by hand through 100-plus columns is slow and error-prone. Type the letters in and the number appears at once, ready to paste into your script.
One honest limit: the tool converts the label, not the data. It does not read your spreadsheet file and it cannot fix a broken formula for you. It simply tells you which letter belongs to which number, so the rest of your work is built on a correct reference. Because it runs entirely in your browser, there is nothing to upload and nothing to install.
A useful habit is to check the letter every time a sheet grows past column Z. The first 26 columns feel obvious, which is exactly why the jump to AA catches people out. Once you are past AZ, the pattern repeats at every multiple of 26, and each new block starts with a fresh first letter. The list view makes that pattern visible, which helps it stick in memory for next time.
How to convert a spreadsheet column
- Type the column number and press To letters, or type the letters and press To number.
- To check a whole block, set the list limit and press Show list.
- Use the confirmed letter in your formula or script.
Frequently asked questions
Why is column 27 AA and not BA? Because there is no zero column. A counts as 1, so the sequence rolls from Z straight to AA, just as 9 rolls to 10 in decimal.
What is the largest column the tool handles? The list view goes up to 500, which is column SF, and single conversions work far beyond that.
Does it work for Google Sheets and Excel? Yes. Both use the same A, B, … Z, AA lettering system.
Is my data uploaded? No. The conversion runs in your browser and nothing leaves the page.
Column letters look trivial until a sheet gets wide, and then they become a quiet source of errors. A two-second check with this converter keeps your formulas pointing at the right data, and the list view turns a confusing system into one you can see at a glance.