Convert XLS to XLSX
What is XLS?
XLS
XLS is Excel's legacy binary format using BIFF (Binary Interchange File Format) within OLE compound document structure. Stores worksheets, formulas, formatting, charts, and macros. No compression—larger files than XLSX. Maximum 65,536 rows and 256 columns per sheet. Gradually replaced by XLSX since Office 2007 but widely compatible with older systems.
- XLS is a spreadsheet format
What is XLSX?
XLSX
XLSX follows Office Open XML standard (ECMA-376)—a ZIP container with XML files for worksheets, shared strings, styles, and calculation chains. Supports multiple sheets, formulas, pivot tables, charts, conditional formatting, and data validation. Replaced binary XLS format in Office 2007. Maximum 1,048,576 rows and 16,384 columns per sheet. Compatible with Excel, LibreOffice Calc, Google Sheets.
- XLSX is a spreadsheet format
Why Convert XLS to XLSX?
✓ Workflow Integration
XLSX format integrates seamlessly with industry-standard software and workflows, ensuring compatibility with professional tools and established production pipelines.
✓ Storage Optimization
Optimize file storage and bandwidth usage while maintaining appropriate quality levels for your specific use case, balancing size efficiency with content requirements.
✓ Future-Proof Format
XLSX ensures long-term accessibility and compatibility as software evolves, providing reliable format support across current and future platform versions.
✓ Simplified Sharing
XLSX format simplifies file sharing via email, cloud storage, and collaboration platforms with guaranteed recipient access and consistent display across systems.
How to Convert XLS to XLSX
- Click the "Start Converting Now" button above
- Upload your XLS file or drag & drop it
- Select XLSX as the output format (pre-selected for you)
- Click "Convert" and processing begins. Download your XLSX file when complete
Features
- ✓ 100% Free Conversion
- ✓ No Registration Required
- ✓ Fast Processing
- ✓ Cross-Platform Compatible
- ✓ Secure Server Processing
- ✓ Auto-Delete After 5 Minutes
- ✓ Batch Processing Available
- ✓ Mobile Friendly
Who Uses XLS to XLSX Conversion?
"I need to convert my XLS files for a specific workflow"
→ XLSX conversion happens in seconds — free, GDPR compliant, and requires no software installation
"I need to convert my XLS files for a specific workflow"
→ XLSX conversion happens in seconds — free, GDPR compliant, and requires no software installation
"I need to convert my XLS files for a specific workflow"
→ XLSX conversion happens in seconds — free, GDPR compliant, and requires no software installation
Frequently Asked Questions
Does batch processing work for XLS to XLSX conversion?
Absolutely. Select multiple XLS files when uploading. Free accounts process 3 files per batch, Premium handles 20 files. All .xlsx outputs download as individual files or combined ZIP archive.
What security measures protect XLS files during conversion?
HTTPS encryption during upload, isolated processing environment, automatic deletion after 5 minutes. Austrian servers under strict EU privacy laws. Zero XLS data retention.
What's your file size limit for XLS to XLSX conversion?
100MB on free tier, 500MB on Premium. Standard XLS files process without problems. Premium tier recommended for professional-sized spreadsheet files.
What's the typical wait time for XLS to XLSX?
Most XLS to XLSX conversions finish in 10-30 seconds. File size and complexity affect speed—simple XLS files convert quickly, while large or intricate spreadsheet content needs additional processing time.
Do I need to install any software?
No! Everything works directly in your web browser. No downloads, no installations, no plugins required. Just upload your file and convert. Works on Windows, Mac, Linux, and mobile devices.
Ready to Convert?
Start converting your XLS files to XLSX now - it's fast, free, and secure!
↑ Convert XLS to XLSX Now