Mbps to MB/s: Megabits to Megabytes per Second
Megabits to megabytes, the factor of eight that makes your download look eight times slower than the plan you bought.
Enter a number.
Lowercase b is bits, capital B is bytes. Internet plans are sold in megabits per second. Download managers report megabytes per second. There are 8 bits in a byte, so a 100 Mbps plan tops out around 12.5 MB/s. Nothing is broken.
The formula
Mbps = MB/s × 8 (exact)
Exact, since a byte is eight bits by definition in every modern context. Note that both sides here use the decimal megabyte of 1,000,000 bytes, which is the convention for transmission rates. Storage capacity is a separate argument, covered on the KB to MB page.
Speed table
| Mbps (megabits/s) | MB/s (megabytes/s) | GB per hour | Note |
|---|---|---|---|
| 10 Mbps | 1.25 | 4.5 | |
| 25 Mbps | 3.12 | 11.2 | HD streaming |
| 50 Mbps | 6.25 | 22.5 | |
| 100 Mbps | 12.50 | 45.0 | common plan |
| 200 Mbps | 25.00 | 90.0 | |
| 300 Mbps | 37.50 | 135.0 | |
| 500 Mbps | 62.50 | 225.0 | |
| 940 Mbps | 117.50 | 423.0 | gigabit real world |
| 1000 Mbps | 125.00 | 450.0 | gigabit nominal |
Why you never get the full number
Even after converting correctly, real throughput sits below the theoretical figure. Every packet carries Ethernet, IP and TCP headers, and those overheads aren't payload. A gigabit link commonly measures around 940 Mbps, roughly 118 MB/s rather than the arithmetic 125.
Wi-Fi adds more: the advertised rate is a radio link rate shared between devices and reduced by distance, interference and protocol overhead. A speed test result below your plan is normal; a result eight times below it usually means you are comparing bits with bytes.
Common questions
Why is my 100 Mbps connection only downloading at 12 MB/s?
Because they are different units. Mbps is megabits per second and MB/s is megabytes per second, and there are 8 bits in a byte. 100 Mbps is 12.5 MB/s, so 12 is close to the theoretical maximum, not a fault.
What is the difference between Mb and MB?
The capital B means bytes and the lowercase b means bits. Connection speeds are sold in bits, file sizes are measured in bytes, and the factor of 8 between them is why the numbers never seem to match.
Why do ISPs advertise in megabits?
It produces a larger number for the same speed. 100 Mbps sounds better than 12.5 MB/s, and bits per second is also the traditional unit for data transmission rates.
Why does gigabit never reach 125 MB/s?
Protocol overhead. Ethernet, TCP and IP each add framing to every packet, so real throughput on a gigabit link typically lands near 940 Mbps, or about 118 MB/s. That is a commonly measured figure, not a specification.
Related converters and guides
Sources
- The relationship between bits and bytes is definitional: one byte is eight bits. Transmission rates conventionally use decimal megabits and megabytes of 1,000,000 units, unlike storage capacity. There is no external conversion factor to cite.