CSV to Excel
Drop your CSV below to get a real .xlsx workbook. The conversion happens inside this browser tab, so the file is never uploaded to a server.
How to convert CSV to Excel
- Choose your CSV file, or drag it onto the box below.
- Optionally name the worksheet.
- Download the .xlsx file and open it in Excel, Numbers or Sheets.
Why leading zeros survive here
Types are decided per column, not per cell. If any value in a column would change when converted — a zip code losing its zero, a long account number becoming 1.23457E+14 — the whole column is written as text. Your identifiers stay identifiers.
Numbers you can still calculate with
Columns where every value converts cleanly are written as real numbers, so totals, averages and charts work as expected without re-typing the column in Excel.
CSV vs Excel: what actually changes
A CSV is plain text holding only values — no formatting, no formulas, no types and a single sheet. An .xlsx file is a compressed bundle of XML that records types, formulas, styling, column widths and as many sheets as you like. Converting CSV to Excel therefore adds structure that was never in the source: the converter has to decide what each column means, which is exactly where most tools quietly damage the data. Going the other way discards everything except the values on one sheet, which is why a CSV export of a workbook loses your formulas.
Why not just double-click the CSV?
You can, and for clean data it is fine. The problem is that Excel guesses a type per cell as it reads, with no way for the file to object. Zip codes lose leading zeros, 16-digit card and account numbers round off into scientific notation, values like 3-10 become dates, and anything over 1,048,576 rows is silently truncated. Converting first, with column-level rules, means the file that opens is the file you had. If you prefer Excel to do the import, use Data → From Text/CSV and set each problem column to Text — this converter simply makes that step unnecessary.
Questions
Will it destroy my leading zeros?
No. This is the main reason to use it rather than opening the CSV in Excel directly. A column is only converted to numbers when every value in it survives exactly, so a zip code column containing 01234 stays as text and keeps its zero.
Is my file uploaded anywhere?
No. The workbook is generated in JavaScript inside your own browser tab. Nothing is sent to a server, stored or logged.
Why does Excel mangle CSVs when I just open them?
Excel guesses a type for each cell as it reads. Long digit strings become numbers in scientific notation, leading zeros are dropped and some values are read as dates. Converting first, with column-level rules, avoids that.
Is the result a real .xlsx file?
Yes, a genuine Office Open XML workbook, not a renamed CSV. It opens natively in Excel, Numbers, LibreOffice and Google Sheets.
Can I choose the worksheet name?
Yes. Set it before converting; it defaults to Sheet1. Excel limits worksheet names to 31 characters, so longer names are trimmed.
Background
For why CSV files lose leading zeros, arrive as one long column, or show strange characters, see what a CSV file is. This page is one of the free CSV converter tools — all of them run in your browser and none of them upload your file.