Mbps Converter — Megabits to Megabytes per Second

Background.

A broadband plan sold as 300 Mbps, and a game launcher that never climbs past about 35 MB/s. It looks as if the provider is delivering a tenth of what you pay for, but nearly all of the gap is notation. The lowercase b in Mbps stands for bits, the capital B in MB/s for bytes, and a byte is eight bits, so 300 Mbps can never show as more than 37.5 MB/s. Software that counts megabytes in steps of 1,024 rather than 1,000 shaves the display to 35.76, and the headers that travel with every packet take a few percent more. The line may be working perfectly.

Network speeds have been quoted in bits per second since the telephone network went digital, when one voice channel carried 8,000 samples a second of 8 bits each: 64 kbps. Files, disks and download counters work in bytes, because that is how data is stored. Each time a speed crosses from one world to the other, someone has to divide or multiply by eight, and the two abbreviations differ only in the case of a single letter.

The converter takes a rate in any of eight units, bits or bytes per second at the plain, kilo, mega or giga scale, and gives it in the unit you choose, with all eight versions listed underneath. The prefixes are the decimal ones the BIPM defines for the SI: kilo is 1,000, mega 1,000,000 and giga 1,000,000,000. Every advertised line rate uses them, so 1 Gbps is exactly 1,000 Mbps and 1 MB/s is exactly 8 Mbps.

What comes out is a change of units, not a speed test. It tells you what a stated rate means in another unit; it cannot tell you how fast a real transfer will run once Wi-Fi conditions, congestion, a slow server or a busy disk join in. For the time a particular file will take, the download-time calculator lets you add an allowance for overhead.

What is mbps converter?

A data rate is an amount of information moved per second. The smallest unit is the bit, a single binary digit; the byte is a group of eight bits, the size NIST describes as the contemporary standard and the unit in which files and memory are counted. Rates are therefore written two ways, in bits per second (bps, kbps, Mbps, Gbps) or bytes per second (B/s, kB/s, MB/s, GB/s), and at the same prefix the byte figure is one eighth of the bit figure. A rate is different from a quantity: 500 MB is a file, 500 MB/s is a speed, and you need a time to get from one to the other. It also helps to separate bandwidth, the capacity a link is sold or signalled at, from throughput, the useful data that actually arrives. Converting units works the same for both but does not close the gap between them.

Which figure you start from changes what the conversion tells you. A plan speed is a sold capacity. A speed-test result is measured delivery, so converting it gives a realistic file rate. The link speed a laptop or phone reports for its Wi-Fi connection is the radio's negotiated signalling rate between device and router; it says nothing about the internet connection behind the router, and the data that actually gets through is well below it.

How to use this calculator.

1. 01Type the rate into Transfer rate exactly as your plan, router, speed test or app shows it. Every unit offered is already per second.
2. 02Set From to the unit the figure came in, checking the case of the b: Mbps, Mb/s and Mbit/s are megabits per second, while MBps and MB/s are megabytes per second.
3. 03Set To to the unit you want to compare against, usually MB/s if you are matching a download counter or Mbps if you are matching an internet plan.
4. 04Read the converted rate, then the list of all eight units below it if you need a different scale, such as Gbps for a network card or kB/s for a slow link.
5. 05If your computer reports sizes in units of 1,024, multiply its MB/s reading by 1.048576 before entering it, because the From options here are decimal.

The formula.

Every unit has a fixed size in bits per second. The bit units are 1 for bps, 1,000 for kbps, 1,000,000 for Mbps and 1,000,000,000 for Gbps. The byte units are eight times larger at each step: 8 for B/s, 8,000 for kB/s, 8,000,000 for MB/s and 8,000,000,000 for GB/s. A conversion multiplies the entered value by the size of the source unit to get bits per second, then divides by the size of the target unit:

result = value × size(from) ÷ size(to)

Going from Mbps to MB/s, that ratio is 1,000,000 ÷ 8,000,000, so you divide by 8. Going from GB/s to Mbps it is 8,000,000,000 ÷ 1,000,000, so 1 GB/s is 8,000 Mbps. Moving between prefixes in the same family changes the figure by a power of 1,000; moving between bits and bytes changes it by 8.

All of these factors are exact by definition, so a value converted out and back returns unchanged. There is no 1,024 anywhere in them. The powers of two belong to the IEC binary prefixes, kibi, mebi and gibi (Ki, Mi, Gi), which NIST recommends for memory-style quantities. One mebibyte per second is 1,048,576 bytes a second, or exactly 8.388608 Mbps, about 4.9% more than a decimal megabyte per second. None of the units offered uses binary prefixes, so a binary reading needs that 1.048576 correction before it goes in.

The conversion also leaves out everything that is not a unit change: the packet headers, error correction, retransmissions and line coding that sit between a link's rated speed and the data you receive. Those are real losses, but they depend on the technology, so no single percentage would be right everywhere.

A worked example.

Frequently asked questions.

References& sources.

1. [1]BIPM SI prefix table defines kilo as 10³, mega as 10⁶ and giga as 10⁹.
2. [2]NIST IR 8354 §2.2 describes the contemporary eight-bit byte and binary digits.
3. [3]IEC explains the standardized distinction among bits, bytes and their symbols in the IEC 80000-13 context.
4. [4]RFC 8670 uses bit-per-second link rates and byte quantities as distinct dimensions in a network standard.
5. [5]NIST's binary-prefix guidance distinguishes decimal SI prefixes from IEC powers-of-two prefixes.