XLS to XLSX Converter
Bring Excel 97–2003 workbooks into the format every current spreadsheet app saves by default. Upload the .xls files, keep all sheets, and download .xlsx workbooks that open without Compatibility Mode.
Data Converter
or drop CSV, TSV, TXT … files here ·
Max 95 MB per file· Up to 20 files· Deleted after 30 minutes
Files are processed on our servers and deleted after 30 minutes.
Character that separates columns in CSV and text files, for both reading and writing. Auto detects it from the input and writes commas.
UTF-8 works for every language. Choose UTF-8 with BOM if Excel on Windows shows garbled accents or Asian characters when opening the CSV.
Excel, ODS and Numbers input: convert the first sheet only, or every sheet (one CSV per sheet in a ZIP, or one JSON key per sheet).
Name of the sheet tab in the new spreadsheet, up to 31 characters.
Array of objects uses column names as keys for every row; array of arrays is more compact and keeps the header as the first array.
Name of the outer element that wraps all rows; each row becomes a <row> inside it.
Used in CREATE TABLE and INSERT statements. Letters, digits and underscores only.
Quoting and column types differ slightly between databases; pick the one you will import into.
Rewrite date cells in one format. ISO (2026-10-18) is safest for databases and code; keep leaves them as they appear in the source.
How to use this tool
- 1
Upload the old workbooks
Drop one .xls or a whole folder's worth, up to 20 files of 95 MB each. Files from Excel 97 through 2003 share one binary layout.
- 2
Keep every sheet
Sheets to convert starts at All sheets on this page, so each tab of the old file becomes a tab in the new one. Switch to First sheet only if the other tabs are scratch work.
- 3
Convert and save
Press Convert to XLSX and download the workbooks, or one ZIP for a batch. Open them in Excel, Google Sheets, Numbers or LibreOffice Calc.
Converting XLS to XLSX moves a workbook from the binary format of Excel 97–2003 to the Office Open XML format introduced with Excel 2007. The rows, columns and sheet names come across; the 65,536-row ceiling goes away; and the file usually gets smaller.
Why old XLS files still turn up
The .xls extension was Excel's default save format from Excel 97 until Excel 2007 replaced it. Accounting archives, lab instruments and inventory systems kept writing it long after, because every reader understood the frozen format. So the files keep appearing: a bank portal export, a supplier's price list reused for years, a decade of monthly reports.
The trouble starts when that file meets current software. Excel opens it in Compatibility Mode, newer functions refuse to save into it, and data libraries such as Python's openpyxl only read .xlsx, so scripts fail on the old binary file. Google Sheets and Numbers import .xls, but every save back is a conversion anyway. Upgrading once, in bulk, ends the back-and-forth. If what you actually need is a flat file for a database import, go straight to XLSX to CSV after this step.
XLS vs XLSX: rows, columns and file size
- rows per sheet in XLS
- 65,536
- rows per sheet in XLSX
- 1,048,576
- columns in XLS (A to IV)
- 256
- columns in XLSX (A to XFD)
- 16,384
The grid is the visible difference: sixteen times as many rows and sixty-four times as many columns. A sensor log or transaction export that was split across sheets to fit the old limit can live on one sheet after the upgrade.
Under the hood the change is bigger. XLS is BIFF8, a binary record stream that only Microsoft fully documented years after release. XLSX is a ZIP archive of XML parts, standardized as ECMA-376 in 2006 and as ISO/IEC 29500 in 2008, which is why so many programs and programming languages can read and write it. The ZIP layer is also why the same data typically takes less disk space as .xlsx.
Macros and formulas need a second look
An .xlsx cannot store VBA macros, and this converter carries cell values rather than live formulas, charts or pivot tables. Keep the original .xls until you have opened the new file and checked that the numbers on your key sheets match.
What people get wrong about upgrading XLS files
MythRenaming the file from .xls to .xlsx upgrades it.
FactThe bytes stay binary BIFF8. Excel then complains that the file format and extension do not match, and other apps refuse it outright.
MythXLS files are unsafe to keep at all.
FactPlain data in an .xls is harmless. The risk sits in macros, which is why Excel blocks macros from the internet by default; an .xlsx simply cannot contain them.
MythOnly Excel 2003 users still need .xls.
FactSome upload portals, older ERP imports and lab software still ask for it, which is the job of XLSX to XLS, the opposite direction.
The two Excel formats side by side
XLS
Microsoft Excel 97–2003 workbook
XLS is the binary spreadsheet format used by Excel from Excel 97 until XLSX replaced it in 2007. It is limited to 65,536 rows and 256 columns per sheet and stores data in a proprietary structure. Many legacy systems, government portals and older banking exports still produce or require XLS. Excel, LibreOffice and Google Sheets can open it.
- Compression
- –
- Transparency
- –
- Animation
- –
- Introduced
- 1997 · Microsoft
XLSX
Microsoft Excel workbook
XLSX is Microsoft Excel's default workbook format since Office 2007, based on the Office Open XML standard. It stores multiple sheets, formulas, formatting, charts, pivot tables and data validation in a ZIP package of XML. It supports over a million rows per sheet and is the default exchange format for business spreadsheets. Google Sheets, LibreOffice and Numbers open XLSX, though macros and advanced features may not carry over.
- Compression
- –
- Transparency
- –
- Animation
- –
- Introduced
- 2007 · Microsoft
People upgrade XLS to XLSX to escape Compatibility Mode, lift the 65,536-row cap and get files that modern apps and scripts read without legacy libraries.
Converting XLS to XLSX: questions
Why does Excel say Compatibility Mode when I open an .xls?
Excel 2007 and later open the old binary format but keep the workbook inside the old limits so it can be saved back as .xls. The title bar shows Compatibility Mode to warn you that the grid stops at 65,536 rows and 256 columns. An .xlsx copy removes that restriction.
Do I need Excel installed to upgrade an XLS file?
No. The conversion runs on the server, so a Chromebook, a tablet or a computer with only LibreOffice can produce .xlsx files, which helps when an IT inventory turns up hundreds of old files.
Will the XLSX file be smaller than the XLS?
Usually, yes. An .xlsx is a ZIP package of XML parts, so repeated text and empty formatting compress well, while .xls stores records uncompressed. Workbooks with lots of text cells tend to shrink the most; one built mostly from embedded images changes little.
What happens to the macros inside an old XLS?
An .xlsx cannot hold VBA code by design; Excel itself refuses to save macros into that extension and points you to .xlsm. Keep the original .xls as the macro source, or copy the modules into a macro-enabled workbook in Excel after converting.
Is it safe to delete the original XLS files afterward?
Open a sample of the new files first and compare totals on key sheets. The data converter writes cell values, so a workbook that depended on live formulas, charts or pivot tables should be checked before the originals go. Files you upload here are deleted from our server after 30 minutes.
- XLSX to XLS ConverterConvert .xlsx workbooks to the legacy .xls format for Excel 2003, older ERP imports and portals that reject XLSX. All sheets kept, 20 files per batch.
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- CSV to XLSX ConverterConvert CSV to an Excel XLSX workbook with leading zeros, long IDs and accented text intact. Comma, semicolon and tab files detected automatically.
- Numbers to Excel ConverterConvert an Apple Numbers spreadsheet to an Excel XLSX workbook that opens on Windows, in Google Sheets and in office portals. Every sheet kept, no Mac needed.
- XLSX to CSV ConverterTurn an XLSX workbook into a clean UTF-8 CSV for Shopify, WooCommerce, Mailchimp, Salesforce or a database import. Formulas become values; dates in ISO.
- CSV to XLS ConverterConvert CSV to XLS, the Excel 97–2003 format older importers and legacy Office installs still require. Auto delimiter detection, up to 20 files at once.