What Does Mbps Mean? Megabits, Megabytes and the Factor of Eight
Mbps stands for megabits per second. It measures how much data your connection can move each second, and it is the number every internet plan is sold on.
The detail that causes nearly all the confusion is this: it is bits, not bytes. There are eight bits in a byte, and file sizes are measured in bytes. So a 100 Mbps connection downloads at about 12.5 megabytes per second at its theoretical best — not 100.
Mbps vs MB/s: divide by eight
To convert your connection speed into the download speed your browser displays, divide by eight.
| Connection speed | Real download rate |
|---|---|
| 25 Mbps | About 3.1 MB/s |
| 50 Mbps | About 6.3 MB/s |
| 100 Mbps | About 12.5 MB/s |
| 300 Mbps | About 37.5 MB/s |
| 500 Mbps | About 62.5 MB/s |
| 1 Gbps (1000 Mbps) | About 125 MB/s |
So when a 1 GB file downloads at 11 MB/s on a 100 Mbps line, nothing is broken. That is the connection running flat out. The convention exists because network engineers have always measured throughput in bits while storage has always been counted in bytes, and neither field was going to change for the other.
The notation matters: Mb and MB are not the same
The capital letter is doing real work. A lowercase b means bits; an uppercase B means bytes.
- Mbps or Mb/s — megabits per second. Connection speed.
- MB/s — megabytes per second. Download rate, eight times smaller.
- MB — megabytes. File size.
Providers advertise in Mbps because the number is eight times larger, which is also why the figure on the bill never matches the figure in the download window.
Kbps, Mbps and Gbps
The prefixes scale by a thousand: 1,000 Kbps is 1 Mbps, and 1,000 Mbps is 1 Gbps. Kbps only turns up now on very slow or heavily throttled connections — if a provider quotes a speed in Kbps, it is slower than a single 1080p video stream needs.
Gbps has become common on fibre plans. A gigabit connection moves about 125 MB per second in theory, though in practice you will rarely see it: Wi-Fi, the device, and the server on the other end all cap out well before the line does. Testing your actual speed over a cable is the only way to know what the line delivers rather than what the plan promises.