Spreadsheets · Windows 10 and 11
Convert CSV to XLSX
Open a CSV file in Octoolo Spreadsheets and it arrives as a proper sheet: columns split on the right separator, numbers you can add up, dates you can sort. Format it, add formulas, and save it as an .xlsx workbook, the CSV to Excel step without Excel.
How to convert CSV to XLSX
- 1
Open the CSV
In Spreadsheets, press Open a file and choose the .csv, or drop it on the start screen.
- 2
Check the columns
The file opens on one sheet named Sheet1, split into columns. Widen a column by dragging its edge, or double-click the edge to fit it.
- 3
Make it a spreadsheet
Bold the header row, keep it in view with Freeze the top row, set number formats, and add totals with Alt =.
- 4
Save as .xlsx
Press Save (Ctrl S). The workbook gets the CSV's name with .xlsx at the end; the CSV itself is not changed.
How the CSV is read
- The separator is guessed from the first line: whichever of tab, semicolon or comma splits it into the most columns. European CSVs with semicolons open as cleanly as American ones with commas.
- Quotes are understood: a field in double quotes can hold commas, line breaks and doubled quotes without breaking the row.
- Numbers become numbers, including negative amounts in brackets and scientific notation. Thousands separators and decimal commas are read the way the language Octoolo runs in writes numbers (Windows' display language, not its regional format setting).
- Percentages and money such as 12%, $19.99, €5 or 40 TL become values with a matching format.
- Dates and times like 2026-10-08, 10/8/2026, 8.10.2026, 8 Oct 2026 or 14:30 become real dates you can sort and subtract. Dates with slashes are read month first or day first to match the language Octoolo runs in (month first for US English); dates with dots or dashes are read day first.
A field that starts with = stays as text, so a formula hidden in a CSV never runs. Empty fields stay empty cells, so the columns stay lined up.
Things to check after opening
- Leading zeros are dropped, as in Excel: a ZIP code 02134 or an ID 000123 becomes 2134 or 123. If those columns matter, keep the CSV for them, or retype the values as text with a ' in front.
- Long numbers, such as card or tracking numbers, become numbers too and show in scientific notation; numbers of more than about 16 digits lose their last digits.
- Accents. Spreadsheets reads CSVs as UTF-8, the standard today. A CSV saved in an older Windows (ANSI) encoding may show wrong characters, such as � where an é should be. Save it again as UTF-8 in the program that made it.
- Codes that look like dates with a year, such as 1-2-23, become dates.
A quick scroll through each column after opening catches all of these before the workbook goes anywhere.
Why turn a CSV into an Excel workbook
CSV is the plain-text format that banks, shops, email tools and databases export: values and separators, nothing more. It cannot hold bold headers, column widths, formulas, number formats or a second sheet. An .xlsx can. Converting is the step from an export to something you can work with and send.
- A bank or card export becomes a budget with a total per category, using SUMIF.
- An order export becomes a report with currency formats and a frozen header row.
- A contact list becomes a tidy sheet before it goes to a colleague who opens everything in Excel.
- Survey answers become a sheet you can sort, count with COUNTIF and print.
Going the other way, for an upload form or a mailing tool, see XLSX to CSV.
Tidying the sheet before you save
A converted CSV looks plain until you give it a little shape. Right-click a column letter and choose Fit the width to the content, or double-click a column's edge. Select the amounts and pick Currency ($), Currency (€) or another format from the number format menu, and use More decimals or Fewer decimals to line up the cents. Sort A to Z puts a list in order, and Find (Ctrl F) with Replace all fixes a repeated typo in every cell at once.
Rename the sheet from Sheet1 to something meaningful by double-clicking its tab; the name is saved in the .xlsx and prints as the heading of a PDF made from the sheet. Then save, and the workbook is ready for anyone who uses Excel. For later edits, see open XLSX without Excel.
Octoolo or an online tool?
| Detail | Octoolo | A typical online tool |
|---|---|---|
| Your files | Stay on your computer | Usually uploaded to the site's server |
| Without internet | Works | Does not work |
| File size | No limit | Often capped on free use |
| Watermarks and ads | None | Common on free plans |
| Cost | $4.99 a month, all 17 apps | Free with limits, or a plan per site |
Questions, answered
My CSV opened in one column. Why?
The separator was not found in the first line, often because the first line is a title rather than headers. Delete that line in a text editor such as Notepad and open the file again.
Does it handle semicolon-separated files?
Yes. Tab, semicolon and comma are all detected from the first line.
Why do accented letters look wrong?
The CSV is probably in an older ANSI encoding. Spreadsheets reads UTF-8, so save the CSV as UTF-8 in the program that made it and open it again.
Can I keep leading zeros?
Not when opening a CSV: digits become numbers. Retype those values with a ' in front, such as '02134, and they stay text with their zeros.
Is the CSV file changed?
No. It is only read. The workbook is a new file with the same name and .xlsx at the end.
Does it work with .tsv and .txt files?
Yes. Tab-separated .tsv files and delimited .txt files open the same way.
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