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CSV to Excel converter
Paste a CSV, see how every cell will be stored, and download a real .xlsx workbook. It runs in this tab, and it keeps the values Excel would otherwise change the moment it opened the file.
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Why not just open the CSV in Excel?
Because Excel decides what each cell is the moment it opens a CSV, and its guesses are destructive. Nothing in a CSV file says “this is text”, so:
| In the CSV | Opened directly in Excel | In the workbook from here |
|---|---|---|
| 02134 (a zip code) | 2134 | 02134 |
| 4242424242424242 | 4.24242E+15, last digit lost | 4242424242424242 |
| MARCH1, SEPT2 | 1-Mar, 2-Sep | MARCH1, SEPT2 |
| 1-2 | 2-Jan | 1-2 |
| 19.90 | 19.9 | 19.90 |
| 1250 | 1250 | 1250, as a number |
The gene-name row is not hypothetical: Excel turning gene symbols such as SEPT2 and MARCH1 into dates corrupted enough published spreadsheets that the HUGO Gene Nomenclature Committee renamed those genes in 2020. And the card-number row loses data for good — an Excel number holds 15 significant digits, so the sixteenth becomes a zero.
The rule here: a cell is stored as a number only when Excel would display exactly what the
CSV says — a plain number with no leading zeros, no trailing decimal zeros, no exponent and at
most 15 significant digits. true and false become Excel
TRUE/FALSE. Everything else is a text cell, shown exactly as written. The preview shades
values that look numeric but stay text, so you can see the decision before you download.
Untick Store safe numbers as numbers to make every cell text.
What the workbook contains
- One sheet, named in the options (Excel allows 31 characters and none of
: \ / ? * [ ]; anything else is replaced). - A header row in bold, frozen so it stays visible while scrolling, with filter buttons on every column.
- Column widths sized to the longest value in each column, up to a limit.
- A real Office Open XML file, compressed where the browser supports it, that opens in Excel, LibreOffice, Numbers and Google Sheets.
The CSV is read with the same parser as the CSV to JSON
converter: quoted fields, embedded commas and newlines, "" escapes and
CRLF line endings all follow RFC 4180, and a tab-separated file is detected from its header
row.
Dates stay text, on purpose
Dates are written as text cells, exactly as they appear. Turning 03/04/2024 into
an Excel date means deciding whether it is March or April, and the right answer depends on
where the file came from — which a converter cannot know. ISO 8601 dates like
2024-03-01 sort correctly as text; to calculate with them, select the column and
use Data → Text to Columns in Excel to convert it with the date order you know is right.
What it is not
It does not write formulas, formats, colours or multiple sheets, and it does not read an existing workbook — for that direction see the Excel to CSV converter. Input up to 2 MB of CSV is handled comfortably; larger files are better split.
Common questions
How do I stop Excel from removing leading zeros?
Store the column as text before Excel opens it. This converter writes any value with a leading zero as a text cell in the .xlsx, so 02134 and 007 open exactly as written. Opening the CSV directly lets Excel convert them to numbers first.
Why does Excel change my long numbers to 4.24E+15?
An Excel number holds 15 significant digits, so a 16-digit ID or card number is rounded and shown in scientific notation. This converter stores values with more than 15 digits as text, which keeps every digit.
Will my numbers still be numbers?
Yes, when they are plain numbers Excel can hold exactly — 42, -3.5, 1250. Values with leading zeros, trailing decimal zeros, exponents or more than 15 digits are kept as text so they are not altered.
Is the file uploaded?
No. The workbook is assembled in your browser and downloaded directly; the CSV never leaves your machine.
Are dates converted to Excel dates?
No, they stay text exactly as written, because a date like 03/04/2024 means different days in different countries. Convert the column in Excel with Text to Columns once you know its date order.
Related
- /excel-to-csv-converter — the reverse: reading an .xlsx back into CSV.
- /excel-sample-data — generating spreadsheet test data, including XLSX, from a schema.
- /csv-to-json-converter — the same CSV, as JSON instead.
- /sample-csv-files — sample CSV files to try it on.
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