What Is a Megabit (Mb)?

And how does it differ from a megabyte (MB)?

A megabit is a unit of measurement for data size, most often used in discussions of data transfer. Megabits are expressed as Mb or Mbit when talking about digital storage, or Mbps (megabits per second) in the context of data transfer rates. All of these abbreviations are expressed with a lowercase 'b.'

Megabits and Megabytes

It takes eight megabits to make a megabyte (abbreviated as MB). Megabits and megabytes sound similar and their abbreviations use the same letters but they don't mean the same thing. It's important to distinguish between the two when you're calculating things like the speed of your internet connection and the size of a file or hard drive.

Illustration of a 1MB cube and its equivalent 8 Mb cubes
Lifewire / Alex Dos Diaz 

For example, an internet speed test can measure your network's speed at 18.20 Mbps, which means that 18.20 megabits are being transferred every second. The same test can say that the available bandwidth is 2.275 MBps, or megabytes per second, and the values are equal. As another example, if a file you're downloading is 750 MB, it's also 6,000 Mb.

Bits and Bytes

A bit is a binary digit or small unit of computerized data. It's smaller than the size of a single character in an email but, for simplicity's sake, think of it as the same size as a text character. A megabit, then, is approximately the size of one million characters.

The formula 8 bits = 1 byte can be used to convert megabits to megabytes and vice-versa. Here are some sample conversions:

  • 8 megabits = 1 megabyte
  • 8 Mb = 1 MB
  • 1 megabit = 1/8 megabyte = 0.125 megabyte
  • 1Mb = 1/8 MB = 0.125 MB

A quick way to figure a conversion between megabits and megabytes is to use Google. Just enter something like "1000 megabits to megabytes" into the search bar.

Why It Matters

Knowing that megabytes and megabits are two different things is important mainly when you're dealing with your internet connection. That's typically the only time you see megabits mentioned.

For instance, if you're comparing service provider internet speeds, you might read that ServiceA can deliver 8 Mbps and ​ServiceB offers 8 MBps. At a quick glance, they may seem identical and you might just pick whichever one is cheapest. However, given the conversion you now know, ServiceB speed is equal to 64 Mbps, which is eight times faster than ServiceA:

  • ServiceA: 8 Mbps = 1 MBps
  • ServiceB: 8 MBps = 64 Mbps

Choosing the cheaper service would likely mean you'd buy ServiceA but, if you needed quicker speeds, you may want the more expensive one instead. That's why it's important to recognize this difference.

What About Gigabytes and Terabytes?

Beyond megabits and megabytes, we enter the territory of much bigger file sizes of gigabytes (GB), terabytes (TB), and petabytes (PB), which are additional terms used to describe data storage but are much larger than megabytes. A megabyte, for example, is just 1/1,000 a gigabyte, tiny in comparison!