CSV to Excel Converter

Convert CSV to a real .xlsx workbook in your browser without losing leading zeros or long IDs, or convert any Excel sheet back to CSV.

Conversion

CSV file

Or paste data below. Files stay on your device.

Delimiter

Or paste CSV data

File encoding

First row

Values in Excel

Text mode guarantees leading zeros, long IDs and codes like 1-2 survive.

Decimal separator in the CSV

Sheet name (optional)

RESULT

Choose a file or paste CSV data to see a preview and download the result.

USING THIS TOOL

How the CSV to Excel Converter helps

Double-clicking a CSV file lets Excel guess: postcodes and customer numbers lose their leading zeros, 16-digit IDs turn into 1.23E+15, product codes like 3-4 become dates and Nordic letters turn into Ã¸. This converter builds a genuine .xlsx file instead, with every value stored exactly as it appears in the CSV, a bold frozen header row with filters and sensible column widths. It also works the other way: pick a sheet from an Excel workbook and download it as a clean CSV.

How values are stored

In the default text mode, every cell is written as text with Excel's text format, so nothing is reinterpreted. In number mode, plain numbers such as 42 or 1234.56 become real numbers you can sum, while values with leading zeros or more than 15 significant digits stay text, because Excel cannot store them as numbers without changing them.

Excel to CSV

Dates are written as YYYY-MM-DD, formulas as their last calculated value and booleans as TRUE/FALSE. Choose a semicolon delimiter and comma decimals for European versions of Excel, and keep the UTF-8 BOM so special characters open correctly.

Frequently asked questions

Is my file uploaded anywhere?

No. The file is read and converted by JavaScript in your browser, and the download is created on your device. Nothing is sent to a server.

Why does Excel remove leading zeros from my CSV?

Excel converts anything that looks like a number when it opens a CSV. Converting to .xlsx with text cells first keeps values such as 00123 exactly as they are.

How large a file can I convert?

Up to about 2 million cells, depending on your device's memory. For larger files, split the CSV first.

Know the limits

Supports .csv, .tsv and .txt input and .xlsx workbooks. Formatting, charts and formulas in .xlsx files are not carried into CSV, which only holds values.