Convert a large CSV to XLSX

Steps

1. Open the CSV in Rowlode; optionally filter, remove duplicates or choose columns.
2. In Export and split choose Excel (.xlsx).
3. Choose what happens above 1,048,575 rows: separate .xlsx files or more sheets in one workbook. You can also split into smaller parts, for example every 200,000 rows.
4. Press Export.

What the Excel file looks like

• A bold header row that stays visible while scrolling, with an AutoFilter.
• Plain numbers (like 42, -3.5) are stored as numbers; values with leading zeros (zip codes, IDs like 00123), long numbers (more than 15 digits, e.g. card or account numbers) and everything else stay text, so nothing is rounded or cut.
• Cells longer than 32,767 characters (Excel’s limit) are shortened, and you are told how many.

Files or sheets?

Several sheets in one workbook are convenient but heavy: a workbook with 3 million rows can take minutes to open in Excel and needs a lot of memory. Separate files open faster. Excel itself may be slow with a sheet of a million rows – that is normal.