Data Transfer Rate Converter
Convert between megabits per second, megabytes per second and every other bit and byte rate.
Runs entirely in your browser. Nothing is uploaded, logged or stored.
100 Mbit/s
12.5 MB/s
Megabyte per second
In every unit
| Unit | Symbol | Value |
|---|---|---|
| Bit per second | bit/s | 100,000,000 |
| Kilobit per second | kbit/s | 100,000 |
| Megabit per second | Mbit/s | 100 |
| Gigabit per second | Gbit/s | 0.1 |
| Terabit per second | Tbit/s | 0.0001 |
| Byte per second | B/s | 12,500,000 |
| Kilobyte per second | kB/s | 12,500 |
| Megabyte per second | MB/s | 12.5 |
| Gigabyte per second | GB/s | 0.0125 |
| Kibibyte per second | KiB/s | 12,207.03 |
| Mebibyte per second | MiB/s | 11.92093 |
| Gibibyte per second | GiB/s | 0.01164153 |
A 100 Mbit/s connection downloads at 12.5 MB/s at best, and that is not the provider cheating: a byte is eight bits, so the number in the browser is one eighth of the number in the contract. Almost every complaint about a connection being slower than advertised is this factor of eight.
How it works
Every unit is expressed in bits per second and conversions go through them. A byte is eight bits exactly, so a byte rate is eight times the bit rate of the same name.
Network equipment and internet contracts are specified in bits — kbit/s, Mbit/s, Gbit/s — because that is what the line actually carries. File managers, browsers and download clients report bytes, because that is what a file is measured in. The lower-case b and the upper-case B are the only thing distinguishing them in writing, which is why they are so often confused.
The binary units are also here. A kilobyte per second is 1000 bytes per second; a kibibyte per second is 1024. Some software labels a rate "KB/s" while actually counting 1024 bytes, so both are listed rather than one being assumed.
Examples
| Case | Input | Result |
|---|---|---|
| A 100 Mbit/s line, as a download reports it | 100 Mbit/s | 12.5 MB/s |
| Gigabit ethernet at full tilt | 1 Gbit/s | 125 MB/s |
| Where the decimal and the binary megabyte part company | 1 MB/s | 0.9536743 MiB/s |
Frequently asked questions
My 100 Mbit/s line downloads at 11 MB/s. Is it faulty?
Probably not. The arithmetic ceiling is 12.5 MB/s, and protocol overhead — TCP headers, IP headers, Ethernet framing — takes a few per cent off that before any of your data moves. Eleven is a normal figure for a healthy 100 Mbit/s connection.
How long will a file take to download?
Divide the size by the rate, in matching units. A 4 GB file over a 100 Mbit/s line is 4000 MB at 12.5 MB/s, so about 320 seconds at the theoretical maximum and rather more in practice. Convert the file size on the data storage page and the rate here, then divide.
Why does the contract say Mbit/s and the download says MB/s?
Because they are measuring different things by convention rather than to mislead. The line is specified in bits because that is the physical signalling rate; the file is measured in bytes because that is how storage is addressed. Both are honest, and eight apart.
What about upload?
Identical arithmetic. The units and the factor of eight are the same in both directions; only the number differs, and on most domestic connections the upload figure is the smaller one.
Good to know
- Every factor used here is an exact definition rather than a rounded measurement, so the only error in a result is the one that comes from displaying it with a finite number of digits.