Data Rate Converter

What this converter does

Internet plans advertise megabits per second, download windows tick along in megabytes per second, and the two are not the same number. This converter moves a data rate between them, across bits and bytes and both the decimal and binary families.

How to use it

• Type your rate into the value box.
• Set From to the unit you have, and To to the unit you want.
• Press Calculate.

The result reads back in plain words, like "100 Mbit/s is equal to 12.5 MB/s." Use Swap to flip the two units, and Reset to clear.

How it works

Everything is referred to the bit per second. A byte per second is 8 bits per second, and each larger unit has its own factor, so the tool converts your rate to bits per second and then out to the target. The two things to keep straight, bits versus bytes and decimal versus binary, are covered just below.

Common data rate conversions

The ones that come up most:

Bits or bytes: why 100 Mbps downloads at 12.5 MB/s

Here is the trap that makes people think their internet is broken. Network speeds are measured in bits per second, but file sizes and download managers are measured in bytes per second, and a byte is 8 bits. So the two never match by the number on the box.

Your 100 Mbps connection is 100 megabits per second. Divide by 8 and that is 12.5 megabytes per second, which is the figure your download shows at its best. A gigabit line (1,000 Mbps) tops out around 125 MB/s. So when a download crawls along at an eighth of your advertised speed, nothing is wrong, the units just changed from bits to bytes. A quick tell: a lowercase "b" means bits (Mbps), an uppercase "B" means bytes (MB/s).

On top of that, this converter carries both the decimal units (kilobit and megabit, based on 1,000) and the binary ones (kibibit and mebibit, based on 1,024), the same two families the Data Size converter uses. And real-world speeds usually run a little below the maximum, because network overhead takes a small cut.

Data rate or data size: which one you need

Data rate and data size are a matched pair with one difference: time. Rate is data per second, the speed of a connection or a transfer. Size is a fixed quantity of data, a file or a disk.

A 50 GB game is a size. Downloading it at 200 Mbps is a rate. So if there is no "per second" involved, you want the Data Size Converter. Speeds and bandwidths belong here.

Questions people ask

References

1. National Institute of Standards and Technology (NIST). Definitions of the SI units: the binary prefixes (kibi, mebi, gibi). https://physics.nist.gov/cuu/Units/binary.html