Convert CSV to XLSX
Free, fast CSV → XLSX. No watermarks, no sign-up.
How to convert CSV to XLSX
1. Upload CSV
Drop your CSV file into the converter above.
2. Confirm XLSX
Output is already set to XLSX. Adjust only if you need to.
3. Download
Convert and download your XLSX file instantly.
Format Details
CSV
CSV (Comma-Separated Values) is a plain-text tabular data format that uses commas to delimit column values and line breaks to separate rows. It is one of the most universally supported data interchange formats, readable by any spreadsheet application, database, or programming language. CSV is ideal for exporting and importing data between different systems due to its simplicity, human readability, and near-universal compatibility.
dataXLSX
XLSX is the default spreadsheet format for Microsoft Excel since Office 2007, built on the Open XML standard and standardized by ISO. It stores worksheets, formulas, charts, pivot tables, and formatting in a compressed ZIP archive of XML files, making it more compact and corruption-resistant than the older XLS format. XLSX is supported by Google Sheets, LibreOffice Calc, Apple Numbers, and virtually every modern data tool.
dataConverting CSV to XLSX: what actually changes
CSV to XLSX is one of the conversions this site performs, but the two formats are not interchangeable containers. Here is what the file keeps, what it loses, and how to get a result you can use.
What .CSV and .XLSX each hold
.CSV is a data format built for analysing, importing or exchanging records, storing rows, columns and value types. .XLSX is a data format built for analysing, importing or exchanging records, storing rows, columns and value types. Converting between them is a decision about which of those two jobs the result needs to do.
What changes in the conversion
Both files belong to the data category, so this is a like-for-like repackage: the same kind of content, stored in a different container. What changes is how .XLSX encodes rows, columns and value types — not what the file is about.
When this conversion is the right one
Reach for .XLSX when the software, device or platform you are sending to expects it — the content is the same data, only the packaging differs. The reverse direction works the same way, so you can always convert back from .XLSX to .CSV using the same tool.
Tips for a clean CSV to XLSX conversion
Start from the original file
Convert the .CSV you started with, not an earlier .XLSX output. Every extra round trip costs quality and can accumulate formatting drift.
Check the real type, not the extension
Text/csv becomes application/vnd.openxmlformats-officedocument.spreadsheetml.sheet. If a file was renamed rather than converted, it will fail to open — rename it back to its true extension before uploading and the conversion will recognise it.
Confirm the structure first
Open the .CSV briefly and check delimiters, headers and encoding. A misplaced separator or a stray quote is the usual reason the output looks wrong even though the conversion succeeded.
Limits worth knowing
Uploads are capped per file (30 MB, or 100 MB for video) and processed temporarily — nothing is kept as a permanent copy. For huge data files, split or compress the source first.
Frequently Asked Questions
How do I convert CSV to XLSX?
Upload your CSV file on Convertek, select XLSX as the output format, then click Convert. Your XLSX file will be ready to download instantly.
Is the CSV to XLSX converter free?
Yes. Converting CSV to XLSX on Convertek is completely free with no watermarks. Fair upload limits apply (typically 30 MB per file).
Is my file kept after conversion?
No. Files are processed temporarily and not stored permanently. Converted downloads are available only in your browser session.
What is the difference between CSV and XLSX?
CSV and XLSX are different file formats with distinct use cases. Converting between them lets you use your file in software or workflows that require the XLSX format.