Know the limit
An Excel sheet holds at most 1,048,576 rows and 16,384 columns. That includes the header row. Many upload forms and email systems have their own, smaller limits, such as 10,000 rows or 5 MB per file. Check what the file is for before you pick a size.
Split by row count
- Open the split tool and add the CSV.
- Choose Every … rows and type the size, for example 1,000,000 for Excel, or 10,000 for an import form.
- Leave Repeat the column names in every file on, so each part opens with its headers.
- Download. CSV parts come in a ZIP, numbered in order: “orders part 01.csv”, “orders part 02.csv”.
Prefer a set number of files? Choose Into … equal files instead.
Split by a column
Often the better question isn't “how many rows” but “whose rows”. Choose One file per value in and pick a column such as State, Sales Rep or Store. You get “Texas.csv”, “Florida.csv” and so on, each with only its rows. Rows with an empty value go into “(blank)”.
How big can the file be?
The split runs in your browser's memory. On a typical laptop, files of a few hundred thousand rows split in seconds. Very large files, in the gigabyte range, can be too much for one browser tab. For those, a command line does it without loading the file into memory. On a Mac or Linux:
tail -n +2 big.csv | split -l 1000000 - part_
That gives files of 1,000,000 rows without headers. Add the header back to each with head -1 big.csv. If this needs to happen regularly, we can set it up for you.
Putting the parts back together
The merge tool does the reverse: add all the parts and download one file.