Why is AA column 27 and not 1?

Spreadsheet columns use bijective base-26, where every position carries a value of 1 to 26 and there is no zero digit. Single letters cover A=1 through Z=26. The next column starts a two-letter run, so AA picks up right after Z at 27, AB is 28, and AZ is 52. If it were ordinary base-26, AA would mean zero, but bijective numbering has no zero, which is exactly why AA lands on 27.

How do I convert a column letter to a number by hand?

Treat each letter as a digit from 1 (A) to 26 (Z) and accumulate left to right: start at 0, and for each letter set total = total times 26 plus the letter value. For AZ that is 1 times 26 plus 26 equals 52. For BA it is 2 times 26 plus 1 equals 53. The tool does this instantly for one value or a whole pasted list, so you never have to track the running multiply yourself.

What number is Z, and what comes after it?

Z is column 26, the last single-letter column. The very next column is AA at 27, then AB at 28, on up to AZ at 52, then BA at 53. After ZZ (702) the three-letter columns begin with AAA at 703. Excel itself stops at column XFD, which is 16384, the rightmost column of a worksheet.

How do I convert a number back into a column letter?

Switch the direction to Number to Letter and type the index. The math subtracts 1, takes the remainder modulo 26 for the rightmost letter, then divides down and repeats. So 27 becomes AA, 52 becomes AZ, and 703 becomes AAA. This is the form you need when a script gives you a 1-based column index and you want the A1-style address to write back into a cell.

Can I paste a cell reference like B7 or $C$3?

Yes. In Letter to Number mode the tool reads the leading letters of an A1 reference and ignores the row, the dollar signs and any Sheet! prefix. So B7 returns 2, $C$3 returns 3, and Sheet1!D2 returns 4. This is handy when you copy a reference straight out of a formula and only care which column it points at.

Where is this actually useful?

Mostly in VBA, Apps Script, Python openpyxl and pandas, where libraries expect a 0- or 1-based column index but humans think in letters. It also helps when reading error messages that cite a column number, planning a wide import, or sanity-checking that column 100 really is CV. Convert once here instead of counting across the header row.

Map a column index from a VBA or Apps Script macro

Your macro returns Cells(1, 703) and you need the A1 address to log or to build a formula string. Switch to Number to Letter, type 703, read AAA, and paste it straight into your code. No more off-by-one mistakes from hand-counting past column Z, and no more guessing whether column 53 is BA or AZ.

Build a column index for openpyxl or pandas

Python libraries want a numeric column, but the spec you were handed lists letters: "totals live in column AB, notes in AZ". Paste the letters one per line, get 28 and 52 back, and feed those straight into your loop. The batch panel turns a whole column legend into an index list in one shot.

Decode a column number from an error message

An import fails with "bad value in column 100" but your viewer shows letters. Type 100, see CV, jump to that column and fix the cell. It beats dragging across a hundred headers and miscounting somewhere in the middle.

Sanity-check a wide spreadsheet layout

Planning a report that runs out to the 40th metric column, you want to know its letter before you write the template. Convert 40 to AN, mark your print range, and confirm the last column lands where you expect rather than discovering it after the export.

Excel Column Converter (Letter to Number and Back)

Turn column letters into numbers and back: A is 1, Z is 26, AA is 27, batch convert, paste A1 refs, copy in one click, all in your browser

Runs locally
Category Format Converter
Best for Turning pasted content or local files into a handoff-friendly format.

Direction:

Column letters or A1 cell (one per line)

Result (6 rows)

A→1
Z→26
AA→27
AZ→52
ZZ→702
AAA→703

Examples:

A is column 1, Z is 26, AA is 27 (not 1) — spreadsheet columns are bijective base-26. Everything runs in your browser.

What this tool does

Free Excel column converter that turns spreadsheet column letters into their numeric index and back, in either direction. Type A and read 1, type ZZ and read 702, type 703 and get AAA. Excel, Google Sheets and every spreadsheet number their columns with a bijective base-26 system, so AA is 27 and not 1, and there is no "zero" letter to trip you up. Paste a whole list, one value per line, and every row converts at once; you can also drop in an A1 cell reference like $C$3 or Sheet1!D2 and the tool pulls out just the column. Switch direction to map numbers back to letters for a script or a macro. One click copies the whole result column, and the shareable URL reproduces your exact list and direction. Everything runs as plain JavaScript in your browser with nothing uploaded.

Tool details

Input: Text + Numbers; The page exposes text boxes, numeric controls, file pickers, or structured inputs depending on the tool.
Output: Live result + Copy; The result area focuses on usable output, with copy, download, or preview actions when supported.
Privacy: Browser-side processing; The main tool logic does not call an external API, so inputs normally stay in the current tab.
Save / share: Shareable URL state; Key settings are encoded in the URL so another person can reopen the same setup.
Performance budget: Initial JS <= 9 KB; No WASM budget is declared, keeping the tool quick to open on mobile.
Best fit: Format Converter · Developer; Category and role tags drive related tools, internal links, and quick fit checks.

How to use

1. Input

Paste or drop your content into the tool panel.
2. Process

Click the button. All processing is local in your browser.
3. Copy / Download

Copy the result or download to disk in one click.

How Excel Column Converter fits into your work

Use it when the main problem is getting content from one practical format into another.

Conversion jobs

Turning pasted content or local files into a handoff-friendly format.
Previewing a conversion before you use it in a larger workflow.
Cleaning small format mismatches without opening a full editor.

Conversion checks

Try a small sample first when the source format is messy.
Check character encoding, separators, and line endings after conversion.
Keep the source until the converted output has been reviewed.

Good next steps

These links move the current task into a more complete workflow.

Real-world use cases

Map a column index from a VBA or Apps Script macro
Your macro returns Cells(1, 703) and you need the A1 address to log or to build a formula string. Switch to Number to Letter, type 703, read AAA, and paste it straight into your code. No more off-by-one mistakes from hand-counting past column Z, and no more guessing whether column 53 is BA or AZ.
Build a column index for openpyxl or pandas
Python libraries want a numeric column, but the spec you were handed lists letters: "totals live in column AB, notes in AZ". Paste the letters one per line, get 28 and 52 back, and feed those straight into your loop. The batch panel turns a whole column legend into an index list in one shot.
Decode a column number from an error message
An import fails with "bad value in column 100" but your viewer shows letters. Type 100, see CV, jump to that column and fix the cell. It beats dragging across a hundred headers and miscounting somewhere in the middle.
Sanity-check a wide spreadsheet layout
Planning a report that runs out to the 40th metric column, you want to know its letter before you write the template. Convert 40 to AN, mark your print range, and confirm the last column lands where you expect rather than discovering it after the export.

Common pitfalls

Reading the columns as ordinary base-26 and expecting AA to be 1 or 0. It is bijective base-26 with no zero digit, so AA is 27. The jump from Z (26) to AA (27) is continuous, not a reset.
Mixing the letter into a number entry. In Number to Letter mode, type 27, not the letter AA. Typing letters there yields an invalid mark; flip the direction first or use the other panel.
Forgetting that Excel uses 1-based columns while many libraries are 0-based. This tool gives the 1-based index that matches the column header (A is 1). For a 0-based API, subtract 1 after converting.

Privacy

Every conversion runs as plain JavaScript inside your browser tab. The column letters, numbers and pasted lists never leave the page and nothing is logged or uploaded. The one caveat: the shareable URL encodes your input list and the chosen direction in the query string, so a link pasted into chat will record those values in the recipient server's access log. If the list is sensitive, use the copy button and paste the text rather than sharing the URL.

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Excel Column Converter (Letter to Number and Back)

What this tool does

Tool details

How to use

1. Input

2. Process

3. Copy / Download

How Excel Column Converter fits into your work

Conversion jobs

Conversion checks

Good next steps

Real-world use cases

Map a column index from a VBA or Apps Script macro

Build a column index for openpyxl or pandas

Decode a column number from an error message

Sanity-check a wide spreadsheet layout

Common pitfalls

Privacy

FAQ

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