CSV to Excel Converter
Turn CSV files into real .xlsx workbooks without mangling codes, IDs or leading zeros.
Drop CSV files here
or select to choose from your device
Files are processed on this device. Nothing is uploaded.
How to use CSV to Excel Converter
- Add one or more CSV or TSV files. The delimiter (comma, semicolon, tab or pipe) is detected and a preview is shown.
- Choose whether plain numbers and ISO dates should become real numbers and dates.
- Select Convert to Excel and download the .xlsx file.
How it works
Opening a CSV directly in Excel is where data gets damaged: 00123 becomes 123, a 16-digit card or order number is rounded to 1.23457E+15, 1E5 turns into 100000 and 3-4 becomes a date. This converter writes a real .xlsx workbook in which every cell already has the right type, so Excel does not guess.
The rule is deliberately cautious. A value becomes a number only if it is a plain number without a leading zero, a plus sign, separators or an exponent, and has at most 15 digits, the most Excel stores exactly. Everything else stays text, exactly as written. The decision is also made per column: if any value in a column looks like a code (a leading zero, a leading plus sign, or more than 15 digits), the whole column stays text, so a ZIP-code column never ends up half numbers and half text. A value becomes a date only in the unambiguous form YYYY-MM-DD (optionally with a time); 03/04/2026 stays text, because it could be March or April.
Quoted fields with commas or line breaks are handled as the CSV standard (RFC 4180) defines. Files are read as UTF-8, so accents and non-Latin scripts arrive intact. Files are read and written by your browser on your device. Nothing is uploaded, so there is no size limit set by us and no copy of your data anywhere else.
Example
A customer export with a zip column (02134), a 19-digit tracking_id and a total column: the ZIP code and tracking ID stay exactly as typed, and total becomes numbers you can sum.
Frequently asked questions
How do I keep leading zeros when converting CSV to Excel?
Use this converter. Values such as 00123 or +44… are written as text cells, so Excel shows them unchanged. Opening the CSV directly in Excel removes the zeros.
Why does Excel show long numbers as 1.23E+15?
Excel stores numbers with 15 digits of precision and switches to scientific notation for long ones, changing the last digits for good. Here, numbers longer than 15 digits are kept as text.
My file uses semicolons or tabs. Will it work?
Yes. The delimiter is detected automatically and shown next to the file name.
Are accents and non-English characters preserved?
Yes, for UTF-8 files, which is what almost all systems export. A file saved in an old regional encoding may show wrong characters; re-export it as UTF-8.
Is there a row limit?
Excel’s own: 1,048,576 rows and 16,384 columns per sheet. Very large files also need enough memory on your device.
Does it work with Google Sheets and Numbers?
Yes. The .xlsx file opens in Excel, Google Sheets, LibreOffice and Apple Numbers.
Limitations
- One sheet per CSV file; files are not merged into one workbook.
- No formulas, colours or column formats beyond numbers, dates and a bold header.
- Files must be UTF-8 text.
- Dates are recognised only as YYYY-MM-DD.
Last reviewed November 9, 2026. How we build and test tools.