Bandwidth Converter
Convert between Mbps, MB/s and everything in between.
What you provide
Result
100 Mbps = 12.5 MB/s
The eight-fold gap between the two families is why a 100 Mbit/s connection downloads at about 12 MB/s and nothing is wrong. Network speeds are quoted in bits per second and file sizes in bytes, a convention that goes back to serial links where the bit was the unit that mattered. Dividing by eight gets you close; expect the real figure to land a little lower still, since protocol overhead takes a few percent before anything useful is delivered.
- Result
- 12.5 MB/s
- In bits per second
- 100,000,000
- Mbit/s
- 100
- MB/s
- 12.5
- 1 GB file takes
- 80.0 s
- 4 GB film takes
- 5.3 min
What this cannot tell you
- Unit arithmetic on the number you type, in your browser. It does not measure your connection.
- Converted figures are theoretical maximums. Real transfers run several percent below them because protocol overhead consumes part of every link.
Take this with you
How this calculation works
Everything is converted through bits per second, which is the unit networks are actually specified in. The eight-fold difference between bits and bytes is where nearly all confusion about connection speeds comes from: internet plans are sold in megabits and download managers report megabytes, so a 100 Mbit/s line showing 12 MB/s is behaving exactly as it should. Two file-transfer examples are shown alongside so the number means something concrete.
What the results mean
- Mbit/s against MB/s
- Eight bits to a byte, so divide by eight to go from the advertised speed to the figure a download shows.
- Decimal against binary
- Network units are decimal, stepping by 1,000. MiB/s is binary and steps by 1,024, which is why it reads about 5% lower than MB/s for the same rate.
- File transfer time
- The theoretical minimum at this rate. Real transfers are slower because of protocol overhead and whatever else shares the link.
Common problems and fixes
- My 500 Mbps connection only downloads at 55 MB/s
- That is very close to correct. Dividing 500 by eight gives 62.5 MB/s as the theoretical ceiling, and losing several percent to protocol overhead lands right about where you are. If the figure is much lower than that, the bottleneck is elsewhere: the server, your Wi-Fi, or a single connection unable to fill a high-latency path.
- Two speed tests report different units
- Check the case of the b. A lowercase b means bits and an uppercase B means bytes, so Mbps and MBps differ by a factor of eight while looking almost identical. It is the single most common source of confusion in networking, and the reason the full forms Mbit/s and MB/s are worth using in anything you write down.
Frequently asked questions
Why are internet speeds sold in bits?
The convention comes from serial communications, where the bit was the natural unit and the byte was not even a fixed size across machines. It stuck, so networks are specified in bits per second while storage is specified in bytes. The mismatch is historical rather than deliberate, though it does make connections sound eight times faster.
How much speed do I lose to overhead?
Typically 3% to 8% on a wired Ethernet connection carrying TCP traffic, once frame headers, acknowledgements and retransmissions are counted. Wi-Fi loses considerably more because airtime is shared and management traffic uses part of it, so a link negotiated at 300 Mbit/s realistically delivers well under half of that.
What speed do I actually need?
Less than most people are sold. Video calls take a few Mbit/s, 4K streaming around 25, and general browsing very little. What matters more is upload capacity and how the connection behaves when several people use it at once, since congestion is felt as lag long before any speed test looks slow.
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