CSV to Excel Converter

This CSV to Excel converter avoids the usual mishaps: columns land in their own cells, leading zeros (ZIP code 02108) and long numbers are kept, numbers and dates become real Excel values. It also turns an XLSX file back into CSV. Everything runs in your browser.

Source: ECMA-376 Office Open XML (SpreadsheetML, ISO/IEC 29500) – Ecma International. Updated: 30 September 2026.

How it is calculated

Double-clicking a CSV file to open it in Excel often brings surprises: ZIP codes like 02108 turn into 2108, product and card numbers into 4.11111E+15, and some values become dates. In countries that use a comma as decimal separator, everything even ends up in column A. This tool writes a real Excel file (XLSX) in which every column is right – and converts Excel files back to CSV when you need it.

How it works

Drop in a CSV file or paste data into the box. The delimiter (comma, semicolon, tab, |) is detected automatically.
Check the decimal separator: US and UK Excel write 1,234.56, much of Europe 1.234,56.
Click “Convert to Excel” and download the XLSX file. The header row is bold, stays visible while scrolling and has filter arrows.
For the other direction, choose an .xlsx file, pick the worksheet and click “Convert to CSV”; several sheets come as one ZIP.

What exactly gets converted

Numbers such as 1,234.50 become real numbers Excel can calculate with.
Dates in ISO format 2026-09-30 (with or without time) become Excel dates. Ambiguous formats like 09/10/2026 stay text on purpose – nobody can tell whether that is September or October.
Text stays text where Excel would mangle it: leading zeros (ZIP codes, customer IDs) and digit strings longer than 15 digits such as card numbers or IBANs – Excel only keeps 15 significant digits and replaces the rest with zeros.
Cells starting with “=” never become formulas.

On the way back to CSV, dates come out as YYYY-MM-DD and numbers with the chosen decimal separator. “UTF-8 with BOM” makes Excel on Windows recognise accented letters right away.

Honest limits

Old .xls files (Excel 97–2003), password-protected workbooks and ODS files cannot be read. Exporting to CSV drops formatting, charts and formulas – the calculated values remain. Excel holds at most 1,048,576 rows and 16,384 columns.

For developers: CSV to JSON turns the same data into JSON, and the XML and CSV validator checks a CSV for errors.

Frequently asked questions

How do I convert a CSV file to an Excel spreadsheet?

Drop the CSV here or paste its content, check the decimal separator and click “Convert to Excel”. You get an XLSX file with every column in its own cells.

Why does Excel put everything in one column when I open a CSV?

Excel expects the delimiter of your regional settings. If they differ from the file (for example commas vs. semicolons), all data lands in column A. The XLSX file created here does not have that problem.

How do I stop Excel from removing leading zeros?

Values with a leading zero such as ZIP code 02108 or customer ID 000123 are written as text into the Excel file, so the zeros stay.

How do I convert Excel to CSV?

Drop the XLSX file here, pick the sheet, set delimiter and decimal separator and click “Convert to CSV”.

Is my data uploaded?

No. Reading and writing the files happens entirely in your browser; the spreadsheet never leaves your device.

Why does Excel show strange characters in my CSV?

Excel on Windows reads unmarked CSV files in the old ANSI encoding. Keep “UTF-8 with BOM” ticked when converting to CSV here, and accents display correctly.

Sources and legal basis

As of: 30 September 2026