How to Convert XLS to XLSX Without Losing Macros (2026)

That said, "convert XLS to XLSX without losing macros" is one of the most-searched Excel questions, so let me give you the complete picture: what's technically happening, what your actual options are, and the exact steps that preserve every VBA module.

Why XLSX Cannot Contain Macros (The Technical Reason)

XLS is the legacy binary format (BIFF8) used by Excel 97–2003. It stores everything — worksheets, styles, and VBA — in a single binary blob using the Compound Document File Format.

When Microsoft introduced the OOXML format family in 2007, they split the file types by capability:

The XLSX specification (ISO 29500 Part 1) explicitly prohibits VBA storage. This isn't a tool limitation — it's a format specification. No tool can create a valid XLSX file that contains VBA macros. Any tool that claims to do so is either:

• Producing an XLSM file and calling it XLSX (extension lie)
• Producing a broken file that Excel will warn about on open
• Simply stripping your macros silently

The Correct Conversion: XLS → XLSM

If you want to modernise your XLS files while keeping macros, the target format is .xlsm. Here are three ways to do it, from easiest to most automatable.

Method 1: Excel Desktop (Recommended for Single Files)

Method 2: LibreOffice Command Line (Batch Conversion)

For batches of 10+ files, LibreOffice headless is reliable. It preserves VBA storage but marks macros as "from a potentially unsafe source" on first open in Excel — a one-time click-through per file.

libreoffice --headless --convert-to xlsm --outdir ./output/ *.xls

Caveats with LibreOffice:

• Complex ActiveX controls may not convert correctly
• Excel-specific API calls in VBA (e.g., Application.ActiveSheet) work fine; LO-specific calls won't exist in XLSM
• Password-protected macros will not convert — you must unprotect in the original XLS first

Method 3: Python with openpyxl + xlrd (Programmatic, Advanced)

If you need to automate this as part of a pipeline, the cleanest approach is to extract macro bytes directly from the XLS binary and transplant them into a new XLSM container.

import xlrd
import zipfile
import shutil
import os

# This is a simplified illustration — full implementation requires VBA storage extraction
# which is available in the MacroKit technical guide

def extract_vba_storage(xls_path):
    """Extract the VBA Storage binary from an XLS file (Compound Document format)"""
    with open(xls_path, 'rb') as f:
        data = f.read()
    # VBA storage is identified by the signature at the Compound Document root
    # Full extraction logic: see MacroKit technical guide
    return data

def transplant_to_xlsm(xlsm_template, vba_bytes, output_path):
    """Inject VBA storage into an XLSM container"""
    shutil.copy(xlsm_template, output_path)
    with zipfile.ZipFile(output_path, 'a') as z:
        z.writestr('xl/vbaProject.bin', vba_bytes)

The full, tested implementation is in the MacroKit research kit — it handles edge cases including workbook protection, UserForm objects, and class modules.

What Online Converters Do to Your Macros

Checking Your Macros After Conversion

Always run this three-step verification on converted files before you delete the originals:

Batch Conversion: 50+ Files

If you're migrating a library of XLS files — common when companies leave SharePoint 2010 or transition from on-premise Excel to Microsoft 365 — the LibreOffice command above scales cleanly to hundreds of files:

#!/bin/bash
# Batch convert all XLS in current directory to XLSM
mkdir -p ./xlsm-output
find . -maxdepth 1 -name "*.xls" | while read f; do
  echo "Converting: $f"
  libreoffice --headless --convert-to xlsm --outdir ./xlsm-output/ "$f"
done
echo "Done. Check ./xlsm-output/"

After batch conversion, run the XLSM Macro Inspector on a sample (10% of files) to verify macro preservation rates before deleting your originals.

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