XLS to XLSX Converter
Convert legacy Excel 97-2003 (.xls) files to modern Excel (.xlsx) format. Free, instant, and private.
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Supports .xls · up to 50MB · or paste a file from your clipboard
Convert a legacy Excel 97-2003 workbook to the modern .xlsx format in your browser. The file is parsed and rewritten locally; nothing is uploaded.
How to Convert XLS to XLSX
- Drop in the .xls file - or several at once, which converts them as a batch and returns a ZIP.
- Let it parse - the legacy binary is read and a new Open XML workbook is built in the page.
- Check the summary - the result panel reports the sheet count and total row count so you can confirm nothing is missing.
- Download - the output keeps the original name with an .xlsx extension.
What crosses over, and what does not
The two formats have almost nothing in common structurally. .xls is a binary record stream inside a compound file; .xlsx is a ZIP of XML parts. So this is a genuine rebuild rather than a rename, and the table below is what that rebuild carries.
| Carried into the .xlsx | Not carried |
|---|---|
| Cell values - text, numbers, booleans, error values | Number formats: dates, currency and percentages arrive as plain numbers under the General format |
| Formulas, rewritten as formulas rather than frozen results | Fonts, fills, borders, alignment and conditional formatting |
| All sheets, with their names and order | Column widths, row heights and frozen panes |
| Merged cell ranges | VBA macros - .xlsx cannot hold them at all |
| Defined names | Charts, images, pivot tables, form controls, print settings |
The number-format line is the one that surprises people. A date cell holding 15 March 2023 stores the number 45000 and a format code that renders it; the value crosses, the format does not, so the converted sheet shows 45000. Select the column in Excel and apply a Date format and the date is back - the data was never lost, only its display rule. The same applies to a currency column arriving as 1234.5 and a percentage as 0.15.
Edge cases
- A .xls that is really HTML or XML.Reporting, payroll and accounting systems often write an HTML table or a SpreadsheetML 2003 document and give it an .xls name - the same files Excel opens with a "format and extension don't match" warning. The contents decide how the file is read, so these convert to a real .xlsx too.
- Password-protected workbooks cannot be read. An encrypted .xls fails with a conversion error, because there is nothing to parse until it is decrypted. See Excel Password Remover for what can and cannot be done about that.
- Very old files. Excel 5.0/95 workbooks and other pre-97 BIFF versions are read where the records are recognisable, but they are far less consistent than BIFF8, and an obscure one may fail outright rather than half-convert.
- Corrupt files are not repaired. If the compound file structure is damaged the parse fails; try Excel Repair first.
- Batch mode is per file. Each .xls becomes its own .xlsx; sheets are never merged across files. Use Excel Merge afterwards if you need one workbook.
- Everything runs in the tab.There is no server step and no queue, but there is also no server's memory to lean on - a very large workbook is limited by the browser.
Why the newer format is worth the move
- Size - .xlsx is a ZIP archive, so a data-heavy workbook is usually much smaller.
- Capacity - 1,048,576 rows and 16,384 columns per sheet, against 65,536 and 256 in .xls.
- Reach - Google Sheets, LibreOffice, Numbers, data pipelines and most upload forms expect Open XML; support for the legacy binary keeps thinning.
- Inspectability - the parts are XML in a ZIP, so a broken file can be examined and often salvaged. A damaged binary stream usually cannot.
When to use a different tool
- You need the legacy format instead: XLSX to XLS.
- The source is a binary .xlsb rather than a legacy .xls: XLSB to XLSX.
- You only want to read the file, not convert it: XLS Viewer.
- The workbook is damaged: Excel Repair or Corrupt Excel Repair.
- You want the data out rather than a newer workbook: Excel to CSV or Excel to JSON.
What's next?
Keep going with one of these tools.
Frequently Asked Questions
The values are intact; the display rule is what was lost. A date in Excel is a serial number, and the number format that renders it as 15/03/2023 is stored separately - this conversion carries the values and the formulas across, not the formats, so every cell arrives as General. Select the column in the converted file and apply a Date format (or Currency, or Percentage) and the correct value reappears. Nothing has to be re-entered.
Yes. Formulas stored in the legacy binary are read, converted to text and written back into the .xlsx, so =VLOOKUP(A2,Sheet2!A:B,2,0) is still a formula afterwards, not a frozen value. Multi-sheet workbooks keep their sheet names and sheet order, and merged cell ranges are carried over.
They do not come across. .xlsx is a macro-free format by definition - Excel stores macros in .xlsm - and the VBA project in a legacy workbook is not carried into the output. If the macros matter, keep the original .xls, or open it in Excel and use Save As with the .xlsm type. Charts, pivot tables, form controls, images and print settings are likewise not written into the .xlsx.
Yes, and this is very common - accounting, payroll and reporting systems routinely write an HTML table or a SpreadsheetML 2003 document and name it .xls, which is why Excel greets it with a 'the file format and extension don't match' warning. The format is detected from the file's contents rather than its name, so both convert to a real .xlsx.
The .xls format itself caps a sheet at 65,536 rows and 256 columns, so nothing you can put in the input can overflow .xlsx, which allows 1,048,576 rows and 16,384 columns. The practical limit is your browser tab's memory, since the whole workbook is parsed and rewritten in it - a file of a few hundred megabytes is where a laptop starts to struggle.
Usually because the legacy file leaned on shared formatting that is not carried across, so its size advantage disappears while the XML overhead of the new format remains. It is more often the other way round, since .xlsx is a ZIP archive. If size matters, run the result through the Compress Excel tool.