You need to send a budget, a price list or a set of results to someone, and you are not sure what they have. Maybe they use Google Sheets, maybe Numbers on a Mac, maybe they will open it on a phone, or maybe it is going into an accounting system rather than to a person. The format you choose decides whether it arrives intact.
Start with what they need to do with it
There are really only three cases.
| They need to… | Send | Why |
|---|---|---|
| Read or print it | Looks identical on every device; nothing to install | |
| Load it into another system | CSV | Plain text that every database and tool reads |
| Work in the spreadsheet | XLSX | Keeps formulas, formatting and every sheet |
Most mistakes come from sending the working file when the other person only needed to read it, or sending a PDF to someone who needed to copy the numbers out.
PDF: when the figures are final
A PDF fixes the layout, so the recipient sees exactly the rows and columns you intended, with no risk of them editing a cell by accident or a formula recalculating differently on their machine. It is the right choice for invoices, quotations, reports and anything that will be printed or signed.
Spreadsheets have no pages, so converting one means deciding where the page breaks go. The Excel to PDF converter sizes columns to their content, repeats the header row on every page so a long table stays readable, and switches to landscape when a sheet has more than six columns. It prints the value in each cell, which for a formula is the result Excel last saved. If the workbook might be stale, open it and recalculate before converting.
CSV: when the data is going somewhere
CSV is the lowest common denominator: one table of text, comma-separated, readable by everything from a bank's import screen to a Python script. It keeps values and nothing else, so formulas become their results, colours and merged cells disappear, and each sheet has to become its own file.
The trap is dates. Excel stores a date as a number of days since the end of 1899, so 1 January 2024 is really 45292, displayed through a date format. A careless export writes the number. The Excel to CSV converter reads each cell's format, recognises dates and writes them as ISO dates such as 2024-01-01, which no system misreads. It writes UTF-8 with a byte order mark so that Excel reopens accented characters correctly, and offers semicolons for recipients whose Excel uses a comma as the decimal separator, as it does across much of Europe.
XLSX: when they need the spreadsheet itself
If the other person needs to change figures, follow formulas or add rows, send the workbook. Not having Excel is rarely a problem now: Google Sheets, LibreOffice Calc and Apple Numbers all open XLSX for free, with formulas and formatting mostly intact. Complex macros, pivot tables and some charts are where compatibility thins out.
Two older formats still turn up. A .xls file is the Excel 97–2003 binary format, which some newer tools refuse; XLS to XLSX upgrades it. An .ods file comes from LibreOffice or OpenOffice and opens in Excel directly. And if what you have is a CSV that someone wants as a proper workbook, CSV to Excel produces an XLSX with numbers stored as numbers rather than text.
A quick check before you hit send
- Open what you are sending, not the original. A conversion only fails silently if nobody looks.
- Check a date column and a long number. Dates turning into five-digit numbers and long IDs turning into
4.53E+15are the two classic corruptions. - Check every sheet made it. A workbook with five tabs becomes five CSV files, or one PDF with five sections.
- Name the file for the recipient.
Q3-prices-2026-10-17.pdfis more useful to them thanBook1 (final) (2).xlsx.