Convert XLSX to CSV

What goes into the CSV

• Only the sheet you are on, from cell A1 to the last row and column in use.
• Results, not formulas. A cell with =SUM(B2:B9) is written as its total.
• Plain numbers. Amounts are written without currency signs or thousands separators, with a dot for decimals: $1,234.50 becomes 1234.5, and 20% becomes 0.2. That is what most programs that import CSV expect.
• Dates and times as they show, in the cell's date format, such as 2026-10-08.
• Text exactly as typed. Fields containing a comma, a quote or a line break are put in double quotes.
• Empty cells become empty fields, so every row has the same number of commas.

Formatting, column widths, other sheets and everything else a workbook holds beyond values are not part of CSV, so they are not in the file. Keep the .xlsx as your working copy.

Encoding and separators

The CSV is saved as UTF-8 with a byte order mark (BOM), with commas between fields and Windows line endings. The BOM is a small marker at the start of the file that tells Excel the text is UTF-8, so names like José, Zoë or Müller open with their accents intact instead of as garbled characters.

Most import tools accept this as it is. Two cases need a moment's thought:

• Systems that expect semicolons, common in countries that write decimals with a comma: choose comma as the separator in the importer, if it lets you.
• Very old or strict tools that do not expect a BOM may show an odd character at the start of the first column name. Most modern ones ignore it.

If an importer shows  in front of the first header, it is reading the BOM as text; telling it the file is UTF-8 usually fixes that.

Where a CSV is needed

• Uploading contacts to an email or newsletter service.
• Importing products or prices into an online shop.
• Bank and accounting imports, and tax tools that read lists of transactions.
• Databases and scripts, where CSV is the common ground between programs.
• Calendar and customer-list imports, such as a list of events or clients.

Before exporting, tidy the sheet: one header row at the top, no totals or notes under the data, no empty rows in between. Importers read every line, and a “Total” row becomes a fake record. Check which columns the importer expects and in what order: renaming a header in the sheet is quicker than matching it up in the importer every time. Need it the other way round? CSV to XLSX turns a CSV back into a workbook.

Checking the CSV before you upload it

A CSV is plain text, so the surest check is to look at it as text. Open it in Notepad or in Octoolo's Text Studio: each row sits on its own line, with the commas and any quotes in plain view. Look for a stray total row, a missing header, and dates in the form the importer asks for.

Empty rows after the data are not written, since the CSV stops at the last row in use. If a column needs cleaning, such as duplicate entries in a mailing list, fix it in the workbook and save the copy again, or tidy the text with remove duplicate lines. For a mailing list, also make sure each email address sits in one column with no spaces around it; remove extra spaces helps there.