Convert CSV to Excel – without data loss (2026 guide)

Why CSV and Excel often misunderstand each other

CSV stands for “comma-separated values” – a plain text file where columns are separated by a delimiter. The format stores no information about character set, delimiter or number format. That is exactly where the trouble starts: Excel has to guess, and it often guesses wrong.

The three most common pitfalls are the delimiter (comma vs. semicolon), the character encoding (UTF-8 vs. Windows-1252) and the number format (dot vs. comma as decimal separator). Knowing these three avoids 95% of all CSV import problems.

The delimiter problem (comma vs. semicolon)

In many European locales the comma is the decimal separator – “1,5” means one and a half. So those programs cannot also use the comma as a column separator and use the semicolon instead. An English CSV, however, separates with a comma. Open a comma CSV by double-clicking in a German Excel and every row lands entirely in column A.

Fix: either import via “Data → From Text/CSV” and pick the delimiter manually, or convert the file to a real XLSX first – then the delimiter no longer matters.

Accented characters and the encoding problem

Modern CSV files are usually UTF-8 encoded. Older Excel on Windows expects Windows-1252. If they do not match, “Müller” quickly becomes “Müller”. A CSV saved as “UTF-8 with BOM” is detected correctly by Excel – the BOM is a small invisible marker at the start of the file that reveals the character set.

Leading zeros and number formats

Postcodes like “01067” or article numbers lose their leading zero when opened directly, because Excel treats them as numbers. Amounts in continental format such as “1.234,56” are also read incorrectly when Excel does not expect the dot as a thousands separator and the comma as a decimal separator.

If you want to keep such columns as text, set the column type to “Text” during import – or convert the file to XLSX beforehand, where data types are stored per column.

Convert CSV to Excel – in the browser, no upload

Instead of fighting import dialogs, you can convert the CSV straight into a finished XLSX file. With the SmashDash spreadsheet converter this runs entirely in your browser – your file is never uploaded or stored.

• Drag the CSV into the converter – delimiter and encoding are usually detected automatically.
• Pick “Excel (.xlsx)” as the target format.
• Click download – the XLSX opens cleanly in Excel, with correct columns and accents.

The other direction: save Excel as CSV

The reverse is often needed too, for example to import data into another program. Pay attention to which delimiter the target system expects, and export as UTF-8 where possible. The converter outputs CSV as UTF-8 by default, so accented characters arrive correctly everywhere.

Frequently asked questions

Why does my CSV land entirely in one column when I open it? Excel expects a different delimiter than the one in the file – usually a semicolon instead of a comma. Import via “Data → From Text/CSV” and choose the delimiter, or convert the CSV to XLSX first.

How do I keep leading zeros on postcodes? Set the column type to “Text” during import. That way Excel does not interpret the value as a number and does not strip the zero.

Is my data uploaded during conversion? No. The SmashDash converter processes the file entirely locally in your browser. There is no server upload.

All SmashDash tools at a glance

SmashDash brings five free spreadsheet tools together in one place – each runs entirely in the browser, with no upload and no account:

• Turn Excel and CSV into interactive, filterable charts. – Turn Excel and CSV into interactive, filterable charts.
• Design charts with your own values and export them as SVG or HTML. – Design charts with your own values and export them as SVG or HTML.
• Convert Excel, CSV and JSON into XLSX, CSV, JSON, Markdown or HTML. – Convert Excel, CSV and JSON into XLSX, CSV, JSON, Markdown or HTML.
• Remove duplicates and empty rows, normalise number formats. – Remove duplicates and empty rows, normalise number formats.
• Merge, split and compress PDFs and extract tables. – Merge, split and compress PDFs and extract tables.

All processing happens locally in your browser – your files are never uploaded, fully privacy-friendly.