In a world of internet speeds and data transfer, terms like Mbps, mb/s and MB/s often are mistaken for the same thing. Both are used to describe data rates, but the difference in capitalization is crucial for understanding which is which.
What’s Mbps (Megabits per Second)?
Mbps stands for megabits per second, and is generally the rate of data speeds used to advertise an internet service provider’s offerings. In digital terms, a bit is the smallest unit of data, and mega stands for one million. Your internet service provider most likely will favor counting in megabits per second - so if your speeds are at 100 mbps, it means your connection can theoretically transmit 100 million bits per second. Mbps is used as a measure of network speed or bandwidth, and network engineers and ISPs alike will use this to quantify speeds and understand how fast data is flowing on a network.
What’s MB/s (Megabytes per Second)?
MB/s (or MBps) stands for Megabytes per second. Here, the uppercase B denotes that we’re dealing with bytes, and not bits. A byte is a group of 8 bits, so the conversion would be 1 Mbps to roughly 0.125 MB/s.
This unit is commonly referred to when discussing file transfer speeds, or disk I/O output. For example, when you download a file, your browser or download manager will most likely show the speeds in MB/s. If you were to transfer a movie file to an external hard drive might sustain 40 MB/s, meaning 40 million bytes a second are written to the drive. Internally, that’s about the same as 320 Mb/s.
| Term | Stands For | Unit Type | Common Usage |
|---|---|---|---|
| MB/s | Megabytes per second | Bytes (uppercase B 1 byte is 8 bits) | File transfer & disk I/O speeds |
| Mbps | Megabits per second | Bits (lowercase b, there are 8 bits in a byte) | Internet & network speeds |
Why The B (or b) Matters
The difference between them ultimately lies in the difference between bits and bytes. A bit (lowercase b) is a single binary digit (0 or 1), whereas a byte (uppercase B) is a group of 8 bits. Because 1 byte is 8 bits, any quantity that’s measured in bytes can be converted to bits by multiplying 8. It’s incredibly common for some people (and some websites) to mix these up, or typo one for the other, leading to some unnecessary confusion.
Always make sure that you pay attention to that one letter difference - it can mean thinking you have a 100-megabit connection versus an 100-megabyte (800 megabit!) connection. Being mindful of the case sensitivity, along with the context, can help you clear up confusion once and for all.
