The fastest way to convert CSV to XLSX

The simplest method is to open your CSV file in Microsoft Excel, then save it as an XLSX file. Excel recognizes CSV format automatically and converts the data into columns and rows. This takes about 30 seconds and requires no additional software.

If you don't have Excel, you can use Google Sheets (free, browser-based) or LibreOffice Calc (free, downloadable). Both open CSV files and save them as XLSX. The steps are nearly identical across all three programs.

This guide covers the three most common routes: Excel on Windows or Mac, Google Sheets, and LibreOffice Calc. Pick whichever program you already have or prefer to use.

Key Takeaways

  • Opening a CSV file in Excel and saving it as XLSX is the fastest method and requires no special knowledge of either format.
  • Google Sheets and LibreOffice Calc both open CSV files and save them as XLSX at no cost, with nearly identical steps to Excel.
  • CSV files sometimes display incorrectly if they contain commas within data fields — Excel usually handles this automatically, but you may need to check the result.
  • The converted XLSX file will look identical to the CSV version but will be recognized as an Excel file by other programs and users.

Converting CSV to XLSX in Microsoft Excel

On Windows: Open Excel. Click File, then Open. Navigate to your CSV file and click it once to select it. Click the Open button. Excel will open the file and display your data in columns. Go to File, then Save As. In the dialog box, find the dropdown that says "Save as type" and click it. Scroll down and select "Excel Workbook (*.xlsx)". Type a name for your file (or keep the existing name — Excel will add the .xlsx extension). Click Save.

On Mac: Open Excel. Click File, then Open. Find your CSV file and double-click it. Excel opens the file automatically. Click File, then Save As. In the dialog box, find the dropdown labeled "File Format" and click it. Select "Excel Workbook (.xlsx)". Type a filename if you want to change it. Click Save.

After you save, your original CSV file remains unchanged. You now have two files: the original CSV and the new XLSX version. You can delete the CSV if you no longer need it, or keep both.

Converting CSV to XLSX using Google Sheets

Go to Google Sheets (sheets.google.com) and sign in with your Google account. Click the "+" button to create a new sheet. Click File, then Open. Click the Upload tab. Drag your CSV file into the upload area, or click "Select a file from your computer" and navigate to it. Google Sheets will open the file as a new spreadsheet.

Once the file is open, click File, then Download. Hover over "Microsoft Excel (.xlsx)" and click it. Your browser will download the XLSX file to your computer's Downloads folder. The original CSV file stays on your computer unchanged.

Google Sheets is useful if you're working on a shared computer or don't have Excel installed. You can also share the Google Sheets version with others and let them download it as XLSX themselves.

Converting CSV to XLSX using LibreOffice Calc

Download LibreOffice Calc from libreoffice.org if you don't have it (it's free). Install it following the on-screen instructions. Open LibreOffice Calc. Click File, then Open. Navigate to your CSV file and click it. Click Open.

A dialog box may appear asking about text encoding and delimiters. In most cases, the default settings are correct — the delimiter should show as "comma" and encoding should show as "Unicode (UTF-8)" or your system's default. Click OK to proceed. Your data will appear in columns.

Click File, then Save As. In the dialog box, find the dropdown labeled "File type" and click it. Scroll down and select "Microsoft Excel 2007-365 (.xlsx)". Type a filename. Click Save. LibreOffice will convert and save the file as XLSX.

What to check after conversion

Open your new XLSX file and scan the data to make sure it converted correctly. Most CSV files convert perfectly — each value stays in its own cell, and columns line up as expected. However, if your CSV contains commas within data fields (for example, an address like "123 Main St, Apt 4"), those fields should have been enclosed in quotation marks in the original CSV file. If they weren't, the conversion may split that data across multiple cells.

If you spot this problem, you have two options: manually fix the cells in the XLSX file (select the misplaced data, cut it, and paste it into the correct cell), or go back to the original CSV file, add quotation marks around any fields that contain commas, and convert again. The second option is faster if many fields are affected.

Check that numbers look like numbers (right-aligned in their cells) and text looks like text (left-aligned). If a column of numbers appears left-aligned, Excel may have read them as text. You can fix this by selecting the column, clicking the yellow warning icon that appears, and choosing "Convert to Number".

When to keep CSV instead of converting

CSV files are smaller than XLSX files and open in almost any program — text editors, spreadsheet software, databases, and programming tools all recognize CSV. If you're sharing data with someone who uses non-Microsoft software, or if file size matters (for example, uploading to a website with a size limit), keeping the CSV format may be better.

XLSX is better if you need to use Excel-specific features like formulas, charts, or multiple sheets. XLSX also looks more polished when you share it with people who expect an Excel file. For most everyday use, either format works fine — pick whichever your team or workflow requires.

Frequently Asked Questions

Will my formulas work after I convert CSV to XLSX?

No. CSV files store only values, not formulas. If your CSV contains calculated data, those numbers will convert fine, but they won't update if you change the source data. If you need formulas, you'll have to recreate them in the XLSX file after conversion.

Can I convert multiple CSV files to XLSX at once?

Not automatically in Excel or Google Sheets. You'll need to convert each file individually. LibreOffice Calc has a batch conversion feature, but it requires using the command line. For most users, converting files one at a time is simpler.

What if my CSV file won't open in Excel?

Try opening Excel first, then using File > Open to navigate to the CSV file instead of double-clicking it. If that doesn't work, try Google Sheets or LibreOffice Calc — they sometimes handle unusual CSV formats better. If none of these work, the file may be corrupted or in a format that isn't actually CSV.

Does the XLSX file need to have the same name as the CSV?

No. You can name the XLSX file anything you want. Many people keep the same name for simplicity (for example, converting "data.csv" to "data.xlsx"), but you can change it during the save step if you prefer.

Can I convert XLSX back to CSV?

Yes, using the same steps in reverse. Open the XLSX file in Excel, Google Sheets, or LibreOffice Calc. Click File, then Save As. Choose CSV format from the dropdown and save. Any formatting or formulas in the XLSX will be lost in the CSV version.