CSV to Excel
Convert a CSV into a formatted .xlsx workbook with bold headers and columns sized to fit, ready to hand to a colleague or send on to a client.
Doing it in Excel instead: How to open a CSV in Excel without breaking it
By Operelio team · Updated October 30, 2026
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What it does
Takes a CSV file and produces a formatted Excel workbook (.xlsx). The output has bold headers in the first row and columns sized to fit the data. It is not a raw paste; it looks like a proper spreadsheet you could hand to a colleague.
When to use it
Use this when you have cleaned data in CSV and need to share it as an Excel file. Common situations: handing a report to a manager who expects .xlsx, sending data to a client, or converting output from another Operelio tool into a formatted spreadsheet. The auto-sized columns and bold headers save you the manual formatting step.
How to use it
Upload your CSV
Drag a .csv file into the upload area, or pick one from your recent files. Comma, semicolon, tab and pipe separated files all work, and the page says which one yours is.
Check the preview
The preview draws the workbook as Excel will open it: the tab, the bold header row, and each column at the width it will have. Search it or jump to a row.
Name the tab, if you like
The tab takes your file's name unless you type another.
Convert
Click Convert to Excel.
How formatting works
The first row is formatted as bold headers. Column widths are auto-sized by sampling the header and the first 100 rows of data to find the widest value in each column. Widths are capped at 50 characters to keep the spreadsheet readable. A longer value is still there in full: widen the column in Excel to see all of it.
The output is always a single-sheet .xlsx file. The sheet is named after your CSV filename by default (for example, pipeline.csv becomes a sheet named pipeline). If the filename contains characters Excel forbids (\ / * ? : [ ]) they are replaced with underscores, and names longer than 31 characters are truncated.
What to know
Every value in your CSV goes into the workbook as text: leading zeros on IDs stay, long numbers aren't turned into scientific notation, dates stay as written, and a value starting with = stays text rather than becoming a formula.
Because every value is text, Excel's SUM skips numbers in the workbook, and Excel may mark them with a small green triangle. To do math on a column, select it and choose Convert to Number. ISO dates (YYYY-MM-DD) sort in the right order as text.
Every row and column in your CSV is written to the workbook as-is, including blank cells and blank rows. If you want those trimmed, clean the CSV before uploading or run Deduplicate afterwards on the downloaded file.
If the CSV is empty (no headers, no rows), the job fails with an error. Add at least a header row to your file and try again.
Row limits apply to every job: 2,000 on Free, 50,000 on Starter, 75,000 on Pro, 150,000 on Agency. If your file is larger, Operelio processes the first N rows up to your plan's limit, and the job's page notes your file's total row count, the limit that was applied, and the number of rows processed.
File size limits are 2 MB on Free, 25 MB on Starter, 35 MB on Pro, and 100 MB on Agency. Uploads larger than the cap are rejected at upload with an error, before the job runs.
How your data is handled
Every cell in your CSV is written to the workbook as text. Nothing is converted to a number, a date or a formula on the way in.
| CSV input | Excel output | Why it matters |
|---|---|---|
| 01234 | 01234 | Leading zeros preserved on ZIPs, SKUs, and account codes. Excel won't silently strip the 0 down to 1234. |
| 07123456789 | 07123456789 | UK mobiles and long numeric IDs stay intact. No scientific notation like 7.12E+09 creeping in from Excel's autodetection. |
| 45000 | 45000 | Numbers come through as the exact text you uploaded. To total a column with SUM, convert it to numbers in Excel first. |
| 2026-01-15 | 2026-01-15 | ISO dates display and sort lexicographically in the right order. Excel won't reformat text cells to '15-Jan-26' or similar. |
| TRUE | TRUE | Boolean-looking values stay as literal text. Excel won't convert them to a checkbox or a 1/0 numeric. |
| café, über-friendly | café, über-friendly | UTF-8 preserves accents and non-Latin scripts. Commas inside cell values are auto-handled by the CSV parser. |
If you want Excel to store dates as real date cells (rather than text that happens to look like dates), convert the column after opening the workbook: select the column, Format Cells > Date. Operelio preserves the exact string you uploaded so your original data is never re-interpreted on the way in.
What the results show
After the job finishes you land on a results page that walks through the output. Expect to see:
Rows and columns
How many rows and columns the workbook holds.
What was saved
A line naming the workbook's one tab, for example: Saved as an Excel workbook with one tab, Sheet1. Headers bold, column widths fitted.
Preview
Every row of the workbook, a page at a time, on every plan. Search it, or go to a row, to spot-check the output before downloading.
Your files
The Files table lists the workbook and your original CSV, each with its rows and the date it's kept until. Download either one. On Starter and up, you can also send the workbook to Files.
Turn a CSV into a formatted .xlsx workbook with bold headers and sized columns.
Frequently asked questions
What plan do I need?
CSV to Excel runs on every plan, including Free. Free covers files up to 2,000 rows and 2 MB; the paid plans raise both.
Can I customize the formatting?
Not currently. The output always has bold headers and auto-sized columns. If you need custom formatting, download the .xlsx and adjust it in Excel.
Does my Excel output have merged cells?
No. Every cell in the CSV becomes an individual cell in Excel. Merged cells are an Excel-only concept; the conversion is one-in, one-out per cell. If you need to merge cells in the output, do it in Excel after downloading.
What happens to blank rows and columns?
Every row and column in your CSV is written to the workbook as-is, including blank cells and blank rows. If you want those trimmed, clean the CSV before uploading or run Deduplicate afterwards on the downloaded file.
How long is my data kept on your servers?
Uploaded files and outputs are retained for 24 hours on Free, 30 days on Starter, 30 days on Pro, and 90 days on Agency. After that, they are permanently deleted from storage, unless you starred them in your library (Starter and above). On Starter and above you can also delete a file yourself at any time from Files.
Can I automate CSV to Excel via an API?
Yes, on the Pro and Agency plans. You get API access to upload files, trigger jobs, and download results programmatically. Pro includes 1,000 API calls per month and Agency 5,000, at 60 requests per minute. Uploads and runs count as calls; reads, like status checks, don't. An upload through the API can be at most 4.5 MB per request, whatever your plan's file size cap. Free and Starter use the web tool only.
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