Convert XLS to XLSX

XLS to XLSX converter that runs entirely in your browser. 100% free, no signup, no upload — your files never leave your device. One-click batch conversion.

Conversions

About formats

XLS

XLS is the legacy binary spreadsheet format used by Microsoft Excel 97 through 2003. It stores tabular data, formatting, formulas, and charts in BIFF binary format, superseded by XLSX in Office 2007.

Developer
Microsoft
Initial release
1987
Compression
Lossless
Color depth
up to 24-bit
Transparency
Yes
Animation
No

Best for

  • Legacy Excel files
  • Compatibility with older Excel versions
  • Tabular data storage

Pros

  • +Compatible with legacy software
  • +Compact binary structure

Cons

  • −Legacy binary format superseded by XLSX
  • −Row and column limits (65,536 rows)
  • −Less open than XML-based formats

XLSX

XLSX is the Microsoft Excel spreadsheet format introduced with Office 2007, based on the Office Open XML standard. XLSX stores worksheets containing rows, columns, formulas, charts, and styling in a ZIP archive of XML parts. XLSX is the most widely used spreadsheet format and is supported by Microsoft Excel, LibreOffice Calc, Google Sheets, and Apple Numbers.

Developer
Microsoft
Initial release
2007
Compression
Lossless
Color depth
up to 24-bit
Transparency
Yes
Animation
No

Best for

  • Financial and data analysis
  • Storing formulas and charts
  • Business spreadsheet sharing
  • Collaborative data in Excel or Google Sheets
  • Formatted tabular data with styling

Pros

  • +Standard Excel spreadsheet format
  • +Stores formulas, charts, and styling
  • +ZIP-based OOXML open standard
  • +Supported by Excel, Google Sheets, LibreOffice Calc, and Numbers

Cons

  • −Not ideal for large pure-data interchange
  • −Complex structure can be slow to parse
  • −Formatting may differ across suites
  • −Overkill for plain data tables

How to convert XLS to XLSX

  1. 1

    Select XLS files from your computer, Google Drive, Dropbox, a URL, or by dragging them onto the page.

  2. 2

    Choose xlsx — or any other format you need as a result (more than 200 formats supported).

  3. 3

    Let the file convert, then download your xlsx file right away.

XLS vs XLSX

PropertyXLSXLSX
CompressionLosslessLossless
DRM supportYesYes
Open formatNoYes

When to use XLS vs XLSX

XLS

  • Legacy Excel files
  • Compatibility with older Excel versions
  • Tabular data storage

XLSX

  • Financial and data analysis
  • Storing formulas and charts
  • Business spreadsheet sharing
  • Collaborative data in Excel or Google Sheets
  • Formatted tabular data with styling

Use cases for XLS → XLSX

  • Legacy Excel files
  • Compatibility with older Excel versions
  • Tabular data storage
  • Financial and data analysis
  • Storing formulas and charts
  • Business spreadsheet sharing
  • Collaborative data in Excel or Google Sheets
  • Formatted tabular data with styling

Frequently Asked Questions

Is converting XLS to XLSX free?
Yes. This XLS → XLSX converter runs entirely in your browser and is completely free — no account, no credits, no watermark.
Which devices and platforms can I use to convert XLS to XLSX?
Any modern device with a current web browser: Windows, macOS, Linux, Android, iPhone and iPad. There is nothing to install — the conversion happens locally.
Are my XLS files uploaded to a server?
No. Files never leave your device. The entire XLS → XLSX conversion runs locally in your browser, so your data stays private.
Can I convert multiple XLS files at once?
Yes — batch conversion is supported. Add as many XLS files as you like and convert them to XLSX in one pass, then download the results together.
What is the maximum file size?
There is no fixed server-side limit because the conversion happens in your browser. Practical limits depend on the available memory and CPU of your device.
Will converting XLS to XLSX lose quality?
No. XLSX is a lossless format (or used in a lossless mode here), so the original data from your XLS file is preserved bit-for-bit in the converted result.
Will transparency be preserved when converting XLS to XLSX?
Yes. Both XLS and XLSX support alpha-channel transparency, so transparent areas of your file are kept unchanged in the XLSX output.
How will the file size change after converting XLS to XLSX?
Both formats use comparable compression, so the XLSX output will be similar in size to your XLS file — typically within 10–20% of each other.

Related Conversions

Specific converters

FREE

100% Free

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SIGNUP

No Signup Required

Start converting immediately without creating an account or sharing email address.

PRIVACY

Private & Secure

Your files never leave your device. All processing is completed locally for maximum privacy.

BATCH

Batch Conversion

Convert multiple files simultaneously to save time. Fast and efficient multi-file queue.

LOCAL

Runs in Browser

Utilizes advanced client-side WebAssembly technology to process files directly inside your tab.

FORMATS

200+ Formats

Supports a wide variety of formats including images, documents, audio, video, and more.

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