Mbps to MB/s Converter
Converts a connection speed in megabits to a download speed in megabytes, and gives the transfer time.
Last updated
Your details
Optional — gives the transfer time.
Result
- Megabytes per second
- 12.5000 MB/s
- Megabits per second
- 100.0000 Mbps
- In MiB/s (binary)
- 11.9209 MiB/s
- Per hour at full rate
- 45.000 GB
- Transfer time
- 6:40
Divide megabits by eight
What most download managers display
5 GB at 12.50 MB/s
100 Mbps…
1 byte = 8 bits, so MB/s = Mbps ÷ 8
100.0000 megabits per second
100.0000 ÷ 8 = 12.5000
12.5000 MB/s
Formula — written step by step
A 100 Mbps connection…
MB/s = Mbps ÷ 8
1 byte = 8 bits
100 megabits per second
100 ÷ 8
12.5 MB/s
Internet speeds are quoted in megabits and file sizes are measured in megabytes. The factor of eight between them is why a "100 Mbps" line downloads a file at about 12 MB/s, and why so many people believe they are not getting the speed they pay for.
A worked example
How long a 5 GB download really takes
- Connection
- 100 Mbps
- File
- 5 GB
- 100 Mbps ÷ 8 = 12.5 MB/s
- 5 GB = 5,000 MB
- 5,000 ÷ 12.5 = 400 seconds
6 minutes 40 seconds, at the full rate
That is the theoretical floor. Protocol overhead, server limits and shared capacity typically add 10 to 20%, so seven or eight minutes is a realistic expectation. A download that takes an hour on this connection is being limited by something other than your line.
How to use this calculator
- Enter your connection speed and its unit — speeds are almost always advertised in megabits.
- Read the megabytes-per-second figure, which is what a download manager displays.
- Add a file size to get the transfer time at the full rate.
- The MiB/s row uses binary megabytes, which is what many operating systems report and is about 5% smaller.
Bits, bytes, and a factor of eight
A byte is eight bits. Network speeds are quoted in bits per second and file sizes are measured in bytes, so converting between them means dividing or multiplying by eight. A 100 Mbps connection transfers at most 12.5 megabytes per second.
The notation is the trap: a lower-case b means bits and an upper-case B means bytes. Mbps is megabits per second; MB/s is megabytes per second. One character separates two figures that differ eightfold, and marketing has little incentive to clarify.
Decimal against binary megabytes
There is a second, smaller discrepancy. Network and storage vendors use decimal prefixes, where a megabyte is 1,000,000 bytes. Operating systems traditionally use binary ones, where the same name means 1,048,576 bytes.
The gap is about 4.9% for megabytes and grows with scale — around 7.4% at gigabytes and 10% at terabytes. This is why a "1 TB" drive shows as roughly 931 GB once formatted. The unambiguous binary units are MiB and GiB, shown here alongside.
Why you never quite reach the advertised rate
Even a perfect connection loses some capacity to protocol overhead. TCP/IP headers, acknowledgements and retransmissions typically consume 5 to 10% of raw throughput before any application data moves.
Beyond that, the advertised figure is the capacity of your line, not a guarantee about the whole path. The server, an intermediate link, Wi-Fi conditions or other devices in the house can each be the limit. When a download runs far below the figure here, the line is usually the last place to look.
Formula & methodology
What this calculator assumes
- Network rates are decimal: 1 Mbps is 1,000,000 bits per second, not 1,048,576.
- Transfer times are theoretical maxima. Protocol overhead alone typically consumes 5–10%, and the far end or the local network is often the real limit.
- The MiB/s row uses the binary megabyte, which is what many download managers display.
Sources
- IEC 80000-13:2008, Quantities and units — Part 13: Information science and technology — bit, byte and the binary prefixes.
Advertised speed against real download rate
| Connection | MB/s | A 1 GB file | A 5 GB file |
|---|---|---|---|
| 10 Mbps | 1.25 | 13 min 20 s | 1 h 6 min |
| 50 Mbps | 6.25 | 2 min 40 s | 13 min 20 s |
| 100 Mbps | 12.5 | 1 min 20 s | 6 min 40 s |
| 500 Mbps | 62.5 | 16 s | 1 min 20 s |
| 1 Gbps | 125 | 8 s | 40 s |
These are theoretical maxima with no overhead. Expect roughly 10 to 20% longer in practice, and considerably longer if the far end is the bottleneck.
Frequently asked questions
Why is my 100 Mbps connection only downloading at 12 MB/s?
It is not slow — that is exactly right. A byte is eight bits, so 100 megabits per second is 12.5 megabytes per second.
What is the difference between Mbps and MBps?
The case of the b. Mbps is megabits per second, MBps or MB/s is megabytes per second, and the second is eight times the first.
Why does my 1 TB drive show as 931 GB?
The manufacturer counts a terabyte as 10¹² bytes; the operating system divides by 1024 three times. The drive holds what was advertised — the two are using different definitions of the same prefix.
Should I expect the full advertised speed?
No. Protocol overhead alone takes 5 to 10%, and the server or your Wi-Fi is often the real limit. Within 20% of the figure here is a healthy connection.