Mbps vs MB/s

One of the most common sources of confusion when measuring internet speed is the difference between megabits and megabytes. While they sound almost identical and use the same letters, they represent two entirely different units of measurement. A bit is a single binary digit (a 1 or a 0), whereas a byte is a larger unit of data consisting of eight bits.

The difference in capitalization is the key to identifying them. A lowercase 'b' stands for bits, while an uppercase 'B' stands for bytes. Therefore, Mbps stands for Megabits per second, and MB/s stands for Megabytes per second. Because there are eight bits in a single byte, one Megabyte is eight times larger than one Megabit.

Understanding this distinction is crucial when analyzing download speeds. When you purchase an internet plan, the speed is advertised in Megabits (Mbps). However, when you download a file in a web browser, the download speed is usually displayed in Megabytes (MB/s). This difference in units makes downloads look eight times slower than your plan speed.

Internet Service Providers measure network speeds in bits because network transmissions are serial. Data travels through network cables as a stream of individual electrical or light pulses, representing single bits of data. Measuring in bits per second provides an accurate representation of the raw transmission rate of the physical medium.

Additionally, measuring in bits is an industry standard that dates back to the earliest days of telecommunications. Modems, dial-up connections, and network cards have always been rated in bits per second. This standard also allows ISPs to advertise larger numbers, which is commercially attractive. A plan advertised as 80 Mbps sounds much faster than one advertised as 10 Megabytes per second.

This naming convention is consistent across all networking hardware. Network cables, switch ports, and Wi-Fi routers are all rated in Megabits or Gigabits per second. It represents the capacity of the pipe, whereas bytes are used to measure the volume of the contents inside the pipe.

Computers store and measure files in bytes, not bits. Your hard drive capacity, operating system files, photos, songs, and documents are all measured in Kilobytes, Megabytes, Gigabytes, or Terabytes. When you download a file, your computer is storing bytes of data to your storage disk.

Because of this, web browsers, game launchers, and application stores display download progress and transfer speeds in Megabytes per second (MB/s). It shows you how quickly the file is actually saving to your device. If a browser displayed speed in Megabits, you would have to perform mental calculations to figure out when your 500 MB file will finish downloading.

This division of terminology means that network engineers work in bits while software developers and consumers work in bytes. Bridge the gap between the two requires a simple mathematical conversion, which explains why a fast speed test result does not match the download speed displayed in your browser.

To convert Megabits per second (Mbps) to Megabytes per second (MB/s), you simply divide the speed by eight. For example, if you run a speed test and get a download speed of 80 Mbps, your maximum file download speed will be 10 MB/s. If you want to convert MB/s back to Mbps, you multiply the speed by eight.

In the real world, your actual download speeds will be slightly lower than this direct mathematical conversion. This is because of network overhead. When data is sent over the internet, it is wrapped in transmission protocols (TCP/IP) that add control data, packet headers, and routing instructions. This overhead consumes about five to ten percent of your total bandwidth.

Additionally, the speed of your download is limited by the server hosting the file. If millions of people are downloading the same update, the remote server will throttle individual transfer speeds to prevent its own network from crashing. In this case, your download speed in the browser will be low, even if your local speed test is fast.