Convert CSV to XLSX with numbers, dates and leading zeros done right
This CSV to XLSX converter turns comma-, semicolon-, tab- or pipe-separated text into a real Excel workbook. Drop one CSV or a whole folder of them, or paste the text, and you get an .xlsx file where amounts are numbers you can add up, dates are dates you can sort, and every CSV becomes its own sheet in one workbook.
Double-clicking a CSV in Excel is a gamble: PIN codes like 011234 and phone numbers lose their first zero, card numbers turn into 4.11111E+15, “03/04/2026” becomes 3 April or 4 March depending on your PC, and Hindi or ₹ symbols arrive garbled. Here the encoding and delimiter are detected for you, every column is checked before anything is converted, and the preview labels each column — number, date (DD/MM), text, codes — so you can see the result before you download it.
Nothing is uploaded. The CSV is parsed by this page’s own RFC 4180 reader and the workbook is written by the open-source SheetJS library, entirely in your browser.
How to convert CSV to Excel
- Drop your CSV files on the upload area, click it to choose them, or open Or paste CSV text and press Add pasted CSV.
- Check each file’s line in the list: it shows the detected delimiter, encoding, size and whether a decimal comma was found. Change Delimiter or Encoding if the preview looks wrong.
- Read the column labels in the preview. If a date column was read the wrong way round, set Dates like 03/04/2026 to day first or month first; list ID or code columns under Always keep as text.
- Choose the header formatting — bold, frozen, filter buttons, fitted widths — and whether you want One workbook or A workbook per CSV.
- Press Convert to XLSX to download the workbook (several workbooks arrive as a ZIP).
CSV to XLSX Converter features
Numbers the way you write them
Western 1,234,567.50, Indian 12,34,567.50, European 1.234.567,50, percentages, (1,500.00) negatives and ₹/$/£/€ amounts become numbers, with a display format that keeps them looking the same — including true lakh/crore grouping.
Dates with a clear day/month rule
ISO 2026-01-15, 15/01/2026, 15.01.2026, 15-Jan-26, Jan 15, 2026 and times are recognised. In Auto mode each column is checked as a whole: a value like 15/01 proves day-first; impossible dates stay as text.
Leading zeros and long codes protected
If any value in a column starts with 0 (PIN, ZIP, employee ID, phone), the whole column stays text. Digit strings longer than 15 characters — card and account numbers — are never rounded.
A finished-looking sheet
The header row is bold and frozen with filter buttons, columns are sized to their content (wide characters such as Chinese or emoji count double), and cells with line breaks wrap.
Many CSVs, one workbook
Each file becomes a sheet named after it. CSVs longer than Excel’s 1,048,576-row limit are split across several sheets automatically.
Encodings detected
UTF-8 with or without BOM, UTF-16, and legacy Windows-1252 files are recognised; Cyrillic, Central European, Japanese, Chinese and Korean encodings can be chosen.
How CSV text becomes Excel cells
Untick Detect numbers, dates, % and TRUE/FALSE to bring every cell in as plain text instead.
| In the CSV | In the workbook | Shown as |
|---|---|---|
1,23,456.78 | number 123456.78 | 1,23,456.78 (Indian grouping) |
1.234,56 (semicolon file) | number 1234.56 | 1,234.56 in your Excel’s style |
12.5% | number 0.125 | 12.5% |
₹1,250.00 | number 1250 | ₹1,250.00 |
15/01/2026 | date 15 January 2026 | 15/01/2026 |
011234, +91 98765 43210 | text | exactly as written |
4111111111111111 | text (more than 15 digits) | exactly as written |
TRUE / false | TRUE / FALSE | TRUE / FALSE |
Day/month order, explained
“03/04/2026” is 3 April in India and the UK but March 4 in the US. In Auto mode the converter looks down each date column: any value whose first number is above 12 (like 15/01/2026) means day first, any value whose second number is above 12 means month first, and a column with no deciding value follows your browser’s language setting. If a column contains both patterns it is left as text rather than guessed. Choosing day or month first yourself applies to every column, and dates that cannot exist in that order, such as 15/01 in month-first mode, stay text so nothing is silently changed.
Time zones in ISO timestamps such as 2026-01-15T10:30:00+05:30 are dropped and the clock time is kept as written, because Excel cells have no time zone.
Limits and related tools
- An .xlsx sheet holds up to 1,048,576 rows and 16,384 columns. Very large files (hundreds of MB) may exceed your browser’s memory.
- Header formatting is applied by editing the workbook’s XML after SheetJS writes it; other styling such as colours isn’t added.
- Going the other way? Use XLSX to CSV. For APIs and code, CSV to JSON and JSON to Excel may suit you better.
CSV to XLSX Converter FAQ
How do I convert CSV to XLSX without losing leading zeros?
Keep “Keep leading zeros” ticked. Any column where a value starts with 0 — PIN codes, ZIP codes, phone numbers, IDs — is stored as text, so 011234 stays 011234 in Excel. You can also name columns under “Always keep as text”.
Can I combine several CSV files into one Excel workbook?
Yes. Drop all the CSVs at once and leave Output on “One workbook — a sheet per CSV”. Each file becomes a sheet named after it.
Why are my dates in the wrong order?
The CSV uses a different day/month order than the converter assumed. Set “Dates like 03/04/2026” to Day first (India, UK, most of the world) or Month first (US) and the preview updates immediately.
My CSV uses semicolons and 1.234,56 — will it work?
Yes. The semicolon is detected automatically and, when values like 1.234,56 or 2,5 appear, the decimal comma is too. The numbers become real numbers in the workbook.
Why does the text look garbled, like é instead of é?
The file’s encoding was guessed wrongly. Pick the right one under Encoding — files from older Windows programs are usually Windows-1252 — and check the preview.
Is my CSV uploaded to a server?
No. Parsing, type detection and writing the .xlsx file all happen in your browser, so the data never leaves your device.