Free Online CSV to Excel Converter

Convert CSV to Excel (XLSX) online for free. Turn comma-separated data into a formatted spreadsheet. Fast, secure — no signup, no software.

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CSV to XLSX — Import a CSV export into Excel-native workflow

CSV → XLSX is what you do when you've exported data from a database, analytics tool, or SaaS report as CSV but need Excel formulas, pivot tables, or charts on top. Preserves the raw data, adds an Excel-native structure. For very large CSV files (>1 M rows) Excel is not the right tool — Google Sheets caps at 10 M cells; better to query directly via BigQuery / Postgres.

CSV to XLSX: where types get guessed

A CSV has no types — every field is text, and the importer guesses. That guess is where data gets damaged: leading zeros vanish from postcodes and product codes, 03/04 becomes a date in whichever order the locale assumes, and long numeric IDs turn into scientific notation. XLSX stores a declared type per cell, so once the guess is made it is baked in.

Convert when you need formulas, multiple sheets or formatting on top of flat data. Check any column of identifiers immediately after converting — that is where the silent damage lands.

CSV vs XLSX: Side-by-side

Technical comparison of the two formats — useful for deciding which to use, or for confirming what changes during conversion.

Property	CSV	XLSX
Full name	Comma-Separated Values	Microsoft Excel (Open XML)
Year introduced	1972	2007
Developer / standard body	IBM (informal)	Microsoft
MIME type	text/csv	application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
File extension	.csv	.xlsx
Compression	None	ZIP-compressed XML
Color / data depth	N/A	N/A
Max dimensions / size	Unlimited	1,048,576 rows × 16,384 columns
Transparency	No	No
Animation	No	No
Standard / specification	IETF RFC 4180	ECMA-376 / ISO/IEC 29500
Best for	Data interchange, database imports, ETL pipelines	Modern Excel spreadsheets, data analysis

CSV to XLSX FAQ

Quick answers about compatibility, quality, metadata handling, and the most common reasons to convert CSV files to XLSX.

How to convert CSV to XLSX without losing formulas or data

Upload your CSV spreadsheet to iFormat and click Convert. Between native formats (XLSX, XLS, ODS) formulas, formatting, and multiple sheets are preserved. Converting to CSV exports cell values as plain rows — formula results are kept, but formatting and extra sheets are not, by design.

Can I open my CSV spreadsheet in Google Sheets after converting to XLSX?

Yes. Convert your CSV to XLSX (XLSX or CSV) and import it into Google Sheets. XLSX preserves formulas and formatting; CSV is universal but carries only values. Google Sheets handles both natively.

How to convert CSV to XLSX online without Excel

iFormat converts CSV to XLSX online — no Excel, LibreOffice, or desktop software needed. Upload, click Convert, and download. It handles tens of thousands of rows without slowing down.

Does CSV to XLSX keep all sheets and tabs?

Between XLSX, XLS, and ODS formats, all sheets transfer intact. When converting to CSV, only the active sheet is captured — convert each sheet separately if your CSV workbook has several tabs.

What is CSV?

CSV is plain comma-separated values, typically used for importing data into any tool. Converting it to XLSX makes the file easier to open, share, or upload where CSV is not supported.

How do I open CSV files?

On Windows: Excel, or any text editor — Notepad shows exactly what is in it. On a Mac: Numbers, Excel, or TextEdit. Opening a CSV in Excel is where data gets damaged: long numbers become scientific notation and leading zeros vanish. Use Data → From Text/CSV and set the column types rather than double-clicking.