Convert CSV to Excel (XLSX)
This free converter turns a CSV file into an Excel .xlsx workbook, detecting the separator and encoding and turning numbers and ISO dates into real cells while leading zeros stay text. The workbook is built in your browser and the CSV is not uploaded. Dates such as 03/04/2024 stay as text instead of being guessed, and cells starting with = are written as text, not formulas.
Did a file not convert correctly? E-mail [email protected], ideally with a small sample file, and it will be fixed.
Key facts
- Input: CSV (.csv). Output: Excel (XLSX) (.xlsx).
- Your files are not uploaded: the work is done in your browser, on your own device.
- File size: no fixed limit; very large files are limited by your device's memory.
- Needs a current browser (Chrome, Edge, Firefox or Safari) on a computer, tablet or phone; nothing to install.
- Free to use, with no sign-up.
Why convert a CSV file to Excel
Double-clicking a CSV file is a gamble. Depending on the language settings of the computer, Excel may put every row into one long column, show ø instead of ø, turn the postcode 0150 into 150 and a long account number into 4.57E+15. This converter reads the CSV the careful way and writes a real Excel workbook (.xlsx), so what you open is what was in the file. It detects the separator (comma, semicolon, tab or pipe) and the encoding (UTF-8, UTF-16 or the Windows-1252 that older Excel versions write), and shows the first rows so you can check that the columns are right before you convert. Numbers become numbers you can sum, ISO dates such as 2024-05-01 become real dates, and everything that only looks like a number, such as codes with leading zeros, stays text. The first row is made bold and stays visible while you scroll.
How to convert CSV to Excel
- Drop your CSV file in the box, or click to choose it.
- Check the columns in the preview; choose another separator if they look wrong.
- Click Convert to Excel and open the downloaded .xlsx file in Excel, Numbers, LibreOffice or Google Sheets.
What changes when you convert
Leading zeros and long numbers stay text
Values such as 0045, 007 or 000123 are written as text cells, so the zeros survive. So are numbers with more than 15 digits, such as card, account or tracking numbers: Excel stores at most 15 significant digits and would replace the rest with zeros. Numbers with a thousands separator, such as 1,250.00, and amounts with a currency sign also stay text, because they could be read in more than one way.
Which dates become Excel dates
Only dates written as year-month-day, such as 2024-05-01 or 2024-05-01 14:30, become date cells. A date like 03/04/2024 means 3 April in Europe and 4 March in the USA, so it is kept exactly as written instead of being guessed. Excel can still turn such a column into dates with Data › Text to Columns.
Decimal commas
In a CSV with semicolons, numbers such as 3,5 are read as 3.5 when most numbers in the file are written that way. In Excel the cell then shows 3,5 or 3.5 depending on your settings, but it is the same number.
Formulas are not run
A cell that starts with = is written as text, not as a formula. That keeps the workbook safe: a CSV from an unknown source cannot slip a working formula into your spreadsheet.
About the formats
CSV
CSV (comma-separated values) is a plain-text table: one line per row, with the cells separated by a comma, a semicolon or a tab. Excel, Google Sheets, Numbers, every database and most programming languages read and write it, which makes it the usual way to move a table from one program to another.
- There is no standard for the separator: Excel uses a comma or a semicolon depending on the language settings.
- Every value is text; whether 0800 is a number or a postcode is up to the program reading it.
- There are no sheets, formulas, colours or column widths, only the values.
- The encoding is not stored in the file; UTF-8 is the safe choice, and Excel needs a BOM to recognise it.
Excel (XLSX)
XLSX is the workbook format of Microsoft Excel since Excel 2007, also written by LibreOffice, Numbers and Google Sheets. Behind the file extension is a zip archive of XML files: one per sheet, plus shared text, styles and formulas.
- A workbook can hold several sheets; a CSV file holds only one table.
- Cells keep their type: numbers, dates and text, so a postcode like 0150 can keep its leading zero.
- A sheet holds at most 1,048,576 rows and 16,384 columns.
- The older .xls format (Excel 97-2003) is a different, binary format.
Frequently asked questions
Is my CSV file uploaded?
No. The file is read and the workbook is built by your browser on your own device. Nothing is sent to a server, which matters for customer lists, payroll data and exports from accounting systems.
Can I turn off the number and date detection?
Yes. Untick the option and every cell is written as text, exactly as it appears in the CSV. That is useful for lists of codes or phone numbers where nothing should be calculated.
How large can the CSV be?
An Excel sheet holds at most 1,048,576 rows and 16,384 columns, and the tool tells you if the file has more. Files up to 200 MB can be read; a few hundred thousand rows take a few seconds on a laptop.
Does the workbook work in Google Sheets and Numbers?
Yes. The .xlsx file follows the standard Office Open XML format, which Google Sheets, Apple Numbers and LibreOffice Calc all open.