Free online CSV to XLSX converter

Data exported from a database, accounting system, or reporting tool often arrives as CSV, while Excel workbooks are required for formulas, formatting, charts, or multi-sheet sharing. Converting it to XLSX makes the table editable as a structured workbook and allows spreadsheet features to be added.

What the CSV format is

CSV (comma-separated values) is a plain-text format in which each line represents a row and delimiters separate fields. The delimiter is not always a comma: exports may use semicolons or tabs because of regional settings or the source program.

Database tools, accounting systems, reporting platforms, scripts, and spreadsheet applications commonly create CSV files for contacts, transactions, product catalogs, sensor readings, and other tabular data. CSV has no standard support for multiple worksheets, formulas, cell formatting, charts, filters, comments, or data validation. It also does not reliably define data types; a field may be interpreted as text, a number, or a date by the program opening it.

What the XLSX format is

XLSX is Microsoft Excel’s XML-based workbook format. It is a ZIP package containing XML parts and can store multiple worksheets, formulas, tables, charts, formatting, filters, comments, hyperlinks, and data validation. Microsoft Excel, LibreOffice Calc, Apple Numbers, and other spreadsheet applications can open it, although feature support can vary.

XLSX is the suitable target when recipients need to edit, calculate, format, filter, or present the data. It is usually larger than the equivalent CSV because it stores workbook structure and metadata, although the package uses ZIP compression. Unlike CSV, it can preserve spreadsheet features after they are added to the workbook.

How to convert CSV to XLSX

With Microsoft Excel

1. Open Excel and choose Data → From Text/CSV. You can also use File → Open → Browse, but the data-import command provides more control over interpretation.
2. Select the CSV file. In the preview or import dialog, choose the actual file encoding and delimiter, such as comma, semicolon, or tab.
3. Set columns containing ZIP codes, account numbers, product codes, telephone numbers, or other identifiers to Text. This prevents values such as 00125 from becoming 125.
4. Load the data into a worksheet, then choose File → Save As and select Excel Workbook (*.xlsx).
5. Reopen the saved workbook and check the headers, row count, dates, numeric values, special characters, and leading zeros before sharing it.

With LibreOffice Calc

1. Open the CSV in LibreOffice Calc. Calc displays an import dialog for text files.
2. Choose the correct character encoding and separator. Confirm that quoted fields, embedded commas, and line breaks appear in the intended columns and rows.
3. Assign sensitive columns the Text type in the import dialog so Calc does not convert identifiers into numbers or dates.
4. Choose File → Save As, select Excel 2007–365 (*.xlsx), and confirm the Excel format if Calc displays a format warning.

Using 101convert.com

You can convert the file on 101convert.com for free without installing software. Upload the CSV, choose XLSX as the output format, start the conversion, and download the resulting workbook. Open the downloaded file locally and verify its contents; do not upload confidential or regulated data unless the service’s current privacy and retention terms are acceptable.

Quality and compatibility limits

Conversion cannot restore information that was never present in the CSV. Formatting, formulas, charts, multiple sheets, comments, named ranges, and data validation must be created after import unless they come from another source. A CSV containing text that begins with =, +, -, or @ may be treated as a formula by spreadsheet software, so inspect untrusted files before enabling or sharing calculated content.

Delimiter, quoting, and encoding determine whether the import is correct. UTF-8 is the preferred encoding for international characters, but some older exports use Windows-1252 or another code page. An incorrect encoding can produce garbled text or replacement characters. A field containing a delimiter, quotation mark, or line break must be quoted according to CSV rules, for example "Smith, Jane"; malformed quoting can shift subsequent values into the wrong columns.

Spreadsheet programs may automatically reinterpret values: 00125 can lose its zeros, long numeric identifiers can be rounded, and strings resembling dates can be reformatted. Import these columns as text rather than correcting them after conversion. XLSX worksheets are limited to 1,048,576 rows and 16,384 columns; data beyond those limits requires a database or another storage format.