How do I convert CSV to XLSX without losing leading zeros?

Open the CSV and inspect the columns in the first pane. A column containing 0012 or a long identifier is kept as text when interpreting it as a number would change its characters. Choose Text for those columns and leave XLSX selected, then Download. The result contains text cells, so Excel does not need to guess their type from a CSV import. Zeros already missing from the source cannot be recovered.

How are numbers, dates and formula-like text handled?

As found uses column-wide type detection for CSV: plain numeric columns, valid ISO dates and TRUE/FALSE can become typed cells. Mixed or ambiguous columns remain text. Override a column with Text, Number, Date or TRUE/FALSE and inspect the preview and conversion notes. Text such as =SUM(A1) becomes a text cell, not an executable formula. The tool does not calculate formulas or infer localized date formats such as 03/04/2026.

Can I convert semicolon-separated CSV or TSV?

Yes. Auto detects the input delimiter, and the input control can force comma, semicolon, tab or vertical bar. Quoted delimiters, doubled quotes and quoted line breaks stay in their cells. Disable First row is a header when the first row is data. XLSX output contains one sheet with the selected table.

Does renaming .csv to .xlsx convert the file?

No. Renaming changes the filename without creating a workbook. Download here writes an actual XLSX package with typed cells. To go in the reverse direction, use the main XLSX to CSV converter and select one worksheet.

Can I convert several CSV files or preserve an existing workbook?

The tool opens one file and exports one selected sheet per download. It does not batch-convert a folder or combine separate CSVs into workbook tabs. It moves values only: formulas from XLSX input use their last saved values, and source styles, charts, merged cells and comments are not carried.

What are the limits for a large CSV?

The table may span up to 10,000,000 cells including blanks. XLSX output must fit Excel’s 1,048,576 rows and 16,384 columns, and browser memory is an additional practical limit. Excel accepts at most 32,767 characters per cell; the tool reports long cells and characters XLSX cannot store. Keep a CSV copy when exact source characters matter.

Is Excel, an account or a file upload required?

No. The source is read and the workbook is written in your browser. Use a current browser on Mac, Windows or Linux. Only converter settings are remembered, not the file. This page starts with XLSX output even if your last visit used another output; you can change the output format afterward.

CSV to XLSX Converter

Turn a CSV or TSV into an Excel-compatible XLSX file without opening it in Excel first. XLSX output is already selected. Open the source, check its delimiter and header, inspect each column type, then download the workbook. Text identifiers such as 0012 stay text; choose Text explicitly for codes that must keep their exact characters.

No file

Sheets, columns and formulas appear here.

Outputone sheet, values only

The converted file appears here.

values only, no formulas

Open an XLSX, CSV or TSV file

Or drop one here, or

Nothing is uploadedFormulas are never runNo account, no sign-up

Sheet

none open

Table

none open

Formula cells

none open

PDF

Letter portrait

Header row

Read CSV as

No file open. Open an XLSX, CSV or TSV file, or the example workbook.

SKU 0012, a text cellCSV to XLSX, then read back
0012 as text, never the number 12
=not-a-formula in a CSV cellconverted to XLSX
a text cell reading =not-a-formula, never a formula
"Bolt, M6" and a two-line cellCSV out, then read back in
quoted on the way out, identical on the way back

Accuracy. Formula cells export the value the file last saved, not a fresh calculation, and a formula with no saved value is listed and left empty rather than guessed. Text such as 0012 or =not-a-formula stays text unless you change its column type. Only cell values move between formats: styles, merged cells, charts and comments are named on screen, not carried.

Common questions

How do I convert CSV to XLSX without losing leading zeros?: Open the CSV and inspect the columns in the first pane. A column containing 0012 or a long identifier is kept as text when interpreting it as a number would change its characters. Choose Text for those columns and leave XLSX selected, then Download. The result contains text cells, so Excel does not need to guess their type from a CSV import. Zeros already missing from the source cannot be recovered.
How are numbers, dates and formula-like text handled?: As found uses column-wide type detection for CSV: plain numeric columns, valid ISO dates and TRUE/FALSE can become typed cells. Mixed or ambiguous columns remain text. Override a column with Text, Number, Date or TRUE/FALSE and inspect the preview and conversion notes. Text such as =SUM(A1) becomes a text cell, not an executable formula. The tool does not calculate formulas or infer localized date formats such as 03/04/2026.
Can I convert semicolon-separated CSV or TSV?: Yes. Auto detects the input delimiter, and the input control can force comma, semicolon, tab or vertical bar. Quoted delimiters, doubled quotes and quoted line breaks stay in their cells. Disable First row is a header when the first row is data. XLSX output contains one sheet with the selected table.
Does renaming .csv to .xlsx convert the file?: No. Renaming changes the filename without creating a workbook. Download here writes an actual XLSX package with typed cells. To go in the reverse direction, use the main <a href="/spreadsheet-converter">XLSX to CSV converter</a> and select one worksheet.
Can I convert several CSV files or preserve an existing workbook?: The tool opens one file and exports one selected sheet per download. It does not batch-convert a folder or combine separate CSVs into workbook tabs. It moves values only: formulas from XLSX input use their last saved values, and source styles, charts, merged cells and comments are not carried.
What are the limits for a large CSV?: The table may span up to 10,000,000 cells including blanks. XLSX output must fit Excel’s 1,048,576 rows and 16,384 columns, and browser memory is an additional practical limit. Excel accepts at most 32,767 characters per cell; the tool reports long cells and characters XLSX cannot store. Keep a CSV copy when exact source characters matter.
Is Excel, an account or a file upload required?: No. The source is read and the workbook is written in your browser. Use a current browser on Mac, Windows or Linux. Only converter settings are remembered, not the file. This page starts with XLSX output even if your last visit used another output; you can change the output format afterward.

Formula cells export the value the file last saved, not a fresh calculation, and a formula with no saved value is listed and left empty rather than guessed. Text such as 0012 or =not-a-formula stays text unless you change its column type. Only cell values move between formats: styles, merged cells, charts and comments are named on screen, not carried.