Convert CSV to XLSX
Upload a .csv or .tsv file and get back a XLSX file. Types are preserved rather than flattened to text. Free, no registration, up to 10MB.
Click to upload or drag and drop
CSV, Excel, SQLite, SQL, DBF (max 10 MB)
How your data is typed in XLSX
Generated from the converter's own XLSX type mapping — this is what it actually emits, not an example.
| Your data | XLSX type |
|---|---|
| Whole number | number |
| Decimal (money) | number |
| Floating point | number |
| True / false | boolean |
| Date | date |
| Date and time | date |
| Short text | text |
| Long text | text |
| Binary data | hex text |
Working from a .csv file
A CSV file carries no header describing itself, so everything about it - the separator, the encoding, whether an empty field means nothing or means zero - has to be worked out from the bytes. That is where the risk in this conversion lives.
- →The separator is sniffed from the first 4 KB across comma, semicolon, tab and pipe, so a semicolon-separated file saved by Excel in a European locale needs no setting.
- →The UTF-8 byte-order mark Excel writes is stripped before the header row is read, so your first column is not named with an invisible character in front of it.
- →Types are decided from the first 10,000 data rows. A value further down that contradicts the type it settled on becomes NULL rather than failing the whole file.
- →The table is named after the file, with spaces and hyphens replaced by underscores: sales report.csv becomes sales_report.
Sheet names and cell types
The workbook is generated rather than exported out of Excel, so every choice in it is one the converter made. The two that show up the moment you open the file are what the sheet is called and what type each cell turned out to be.
- →The sheet takes the table's name cut to 31 characters, which is Excel's own limit for a tab, while the workbook file keeps the name in full - so a long table name is complete in the file name and shortened on the tab inside it.
- →Dates and timestamps become genuine date cells, formatted yyyy-mm-dd and yyyy-mm-dd h:mm:ss, rather than strings that merely look like dates. Sorting and date arithmetic work on them with no conversion step first.
- →A text column of digits stays text: a value like 01234 is written into a string cell, and Excel shows it as it was stored instead of dropping the zeros the way it does when the same data is opened from a CSV.
Reading CSV
- →Leading zeros are preserved. A column containing 01234 is kept as text, never turned into the number 1234.
- →An empty cell becomes NULL, not an empty string — the two mean different things once the data is in a database.
- →Dates are only treated as dates when the format is unambiguous. 03/04/2025 could be March 4th or April 3rd, so it stays text unless another value in the column settles it.
Writing XLSX
- →One file per table. Booleans stay booleans and numbers stay numbers.
- →Excel has no fixed-point type, so decimals become numbers — use a database target if exactness matters.
What you get
A ZIP containing <table>.xlsx. If anything about your data needed a judgement call, a _warnings.txt explains it.
Questions
- Is converting CSV to XLSX free?
- Yes. Files up to 10MB convert free with no account. There is a limit of five conversions per day per IP address.
- Will my CSV data keep its types in XLSX?
- Yes — that is the point. Whole numbers, decimals, dates and booleans are mapped to real XLSX types rather than everything becoming text. The mapping table above shows exactly what you get.
- Do you store my file?
- No. The file is written to a temporary directory, converted, and the directory is deleted as soon as your download has been sent.