How to use the excel (xlsx) to csv converter
- Choose an .xlsx file or drop it on the box. It is opened on your device. If the workbook has several sheets, pick the sheet you want, and hidden sheets are marked as hidden.
- Check the preview and the counts of rows, columns and filled cells. The notes under the counts tell you if any cells hold formulas, show errors, or start with a character that spreadsheet programs treat as a formula.
- Choose the separator, the line ends, whether to add a UTF-8 byte order mark so Excel shows accents correctly, and whether to put an apostrophe before cells that start with = + - or @.
- Press Download .csv. With several sheets the sheet name is added to the file name.
What comes out of a workbook
A cell that Excel shows as 3/14/2026 is stored as the number 46095 with a date format. The converter writes it as 2026-03-14. A time cell stored as 0.75 comes out as 18:00:00, and a date with a time such as 45000.5 becomes 2023-03-15 12:00:00. A boolean cell comes out as TRUE or FALSE.
A formula cell that adds 1 and 2 and was last saved with the result 3 comes out as 3, and a cell showing #DIV/0! comes out as #DIV/0!. A cell that holds a long number such as 12345678901234 comes out with all its digits and no scientific notation.
What the converter reads
An .xlsx file is a ZIP archive of XML parts. The converter reads the workbook part for the sheet list, the shared strings for text, the styles to tell dates and times from other numbers, and the sheet part for the cells. Text, inline text, rich text, numbers, booleans, error cells, and the last saved result of formulas are supported, in both the 1900 and 1904 date systems.
Dates use Excel's own rule, including its well-known quirk that it treats 1900 as a leap year, so serial number 60 is shown as 1900-02-28. The tool reads the value that was stored, not how it was displayed, so a number shown as 12% comes out as 0.12 and a number shown with a currency sign comes out without it.
What it does not do
Formulas are not calculated: the value saved with the file is used, and a workbook that was never calculated may show empty cells. Pictures, charts, comments, conditional formats, styles and merged cells are not carried over, and a merged range shows its value only in the top left cell. Older .xls files, binary .xlsb files, OpenDocument files and password protected workbooks are recognized and refused with an explanation rather than read wrongly.
Macros in .xlsm files are never run. To go the other way, use the CSV to Excel converter, and for Excel date serial numbers on their own, see the Excel date serial number converter.
Opening the CSV safely
A cell that starts with =, +, - or @ can be run as a formula when a CSV file is opened in a spreadsheet program. If the workbook came from someone you do not know, tick the apostrophe option, which puts a quote mark in front of such cells so they are shown as text. It changes those cells, which is why it is off by default.
Assumptions and limits
- Cells are written as the stored value. Numbers use the shortest text that gives the same number, so 0.1 stays 0.1 and large whole numbers keep every digit.
- Date detection relies on the number formats saved in the workbook. A date typed into a cell with a General format is just a number and is written as one.
- A sheet with more than 3,000,000 filled cells is read only in part, with a message, and files over 25 MB are refused.
- Empty rows and columns between filled cells are kept so every value stays in its original position.
Frequently asked questions
Why is a date in my CSV a number like 46095?
That would mean the cell did not carry a date format in the workbook, so it is only a number. Cells with a date or time format are converted to readable text such as 2026-03-14.
Does it work with .xls files from older versions of Excel?
No. Open the file in Excel or another spreadsheet program, choose Save As and pick the .xlsx format, then use the new copy here.
Is my workbook uploaded anywhere?
No. The file is opened by code in your browser and the CSV is created on your device. A sheet is read only when you pick it.
Why does the CSV show strange characters for accents in Excel?
Excel needs a UTF-8 byte order mark to know the file is UTF-8. Leave that option ticked if you plan to open the CSV in Excel.