How to use the csv to excel (xlsx) converter
- Paste CSV text into the box, or choose a .csv or .txt file. The separator is detected for you, or you can choose comma, semicolon, tab or pipe yourself.
- Check the preview of the first rows and the count of rows and columns. Choose whether the first row is a header (it is then bold and frozen), whether plain numbers and dates are stored as real numbers and dates, and whether column widths fit the content.
- Give the sheet a name if you like, then press Download .xlsx. The file is named after your CSV file.
- Open the workbook in Excel, Numbers, LibreOffice or Google Sheets. Numbers can be summed, dates can be sorted, and text such as part numbers keeps its leading zeros.
Four columns, three rows
The sample has the header Name, Qty, Price, Ordered and three rows. Pens have a quantity of 12, a price of 3.5 and the date 2026-03-14, which Excel stores as the serial number 46095. The next two dates are 46096 and 46097. The third name, "Tape, clear", has a comma inside quotes, so it stays one cell. The workbook has 4 columns and 4 rows including the header.
A part number such as 007 stays text so the zeros are kept, and a value such as 12345678901234567 with more than 15 digits also stays text, because Excel only keeps 15 significant digits of a number and would otherwise change the last digits.
What gets converted to numbers and dates
Only plain numbers are stored as numbers: an optional minus sign, digits with no leading zero, and an optional decimal part, with at most 15 significant digits. Values with a currency sign, a percent sign, thousands commas, a plus sign, an exponent or a leading zero stay as text, because turning them into numbers would change what they mean or lose digits.
Dates are recognized in the ISO form year-month-day, optionally followed by a time, such as 2026-03-14 or 2026-03-14 09:30:15. They are stored as Excel dates with a matching display format. Dates before March 1, 1900 and impossible dates such as 2026-02-30 stay text. Both conversions can be turned off if you want every cell kept exactly as text.
What is in the file
The workbook is a standard .xlsx package built from XML parts: one sheet, text stored inside the cells, a small style sheet for the bold header and the date formats, and nothing else. No macros, formulas, links or external references are ever written, and text that begins with = or @ is stored as text, never as a formula, so a hostile CSV cannot run anything when opened.
It was checked by reading the files back with a separate spreadsheet library, which found the same text, numbers, dates, bold header, frozen pane and column widths. To go the other way, use the Excel to CSV converter. To combine or split CSV files first, use CSV merge and split.
Assumptions and limits
- The CSV is read by a strict reader: quoted fields may hold commas, quotes written twice and line breaks, and an unclosed quote is reported instead of guessed.
- A sheet holds at most 1,048,576 rows and 16,384 columns, and cells longer than 32,767 characters are cut off with a message. Files over 25 MB or 3,000,000 cells are refused.
- Control characters that XML cannot hold are replaced by the Unicode replacement character, and blank cells are left empty.
- Only one sheet is created and no styling beyond the header and date formats is applied.
Frequently asked questions
Why did my number with leading zeros stay as text?
A number cannot keep leading zeros, so storing 007 as a number would turn it into 7. It stays text, which is what you want for part numbers, zip codes and similar codes.
Does the converter send my CSV to a server?
No. The file is read and the workbook is built by code in your browser tab, and the download is created on your device.
Can I get several sheets in one workbook?
Not in one step. This tool makes a single sheet. Convert each CSV separately and move the sheets together in your spreadsheet program, or merge the files first with the CSV merge tool.
Why are my semicolon-separated European files not splitting into columns?
Leave the separator on Detect it, or choose Semicolon. The preview shows the columns before you download, so you can see the split is right.