Mbps to MB/s Converter

Why a 100 Mbps plan downloads at 12.5 MB/s — convert internet speeds between bits and bytes.

Conversion table

Speed	In MB/s
1	0.125 MB/s
2	0.25 MB/s
3	0.375 MB/s
4	0.5 MB/s
5	0.625 MB/s
10	1.25 MB/s
15	1.875 MB/s
20	2.5 MB/s
25	3.125 MB/s
30	3.75 MB/s
40	5 MB/s
50	6.25 MB/s
60	7.5 MB/s
70	8.75 MB/s
75	9.375 MB/s

🔢 Divide by eight

8 Mbps1 MB/s
50 Mbps6.25 MB/s
100 Mbps12.5 MB/s
1 Gbps125 MB/s

Reading a speed test honestly

The letter is the whole story: lowercase b is a bit, uppercase B is a byte. Mbps and MBps differ by a factor of eight, and marketing always picks the bigger-looking one.
Speed tests report Mbps because that is what the line does; download managers report MB/s because that is what the file does. Both can be right at once.
Expect to land a few percent under the arithmetic. TCP/IP headers, retransmissions and Wi-Fi overhead all ride on the same wire as your file.
If a gigabit plan tops out near 12 MB/s, suspect a 100 Mbps Ethernet port or an old cable before blaming the provider.

One byte, eight bits, and the whole confusion

A bit is a single one or zero. A byte is the group of eight bits that computers actually store and address, which is why file sizes are quoted in bytes. Network links, on the other hand, are measured in bits per second, because a wire moves signal transitions and does not care where one byte ends and the next begins. So the two industries measure the same traffic with rulers that differ by a factor of eight, and every conversion between an internet plan and a download window is exactly that division: Mbps ÷ 8 = MB/s.

Why providers advertise in bits

Telecommunications measured signalling rate in bits per second long before home broadband existed, and the convention stuck through modems, DSL, cable and fibre. There is also a plainer reason it never changed: 1,000 Mbps reads better on a billboard than 125 MB/s, even though they are the same connection. Nothing in the practice is dishonest — Mbps is the correct unit for a link, and regulators such as the FCC report broadband performance in Mbps — but it does mean the number on the bill is never the number in the download bar.

Why you rarely hit the exact number

Protocol overhead. Ethernet, IP and TCP headers travel with every packet, so 5–10% of the raw line rate carries addressing rather than your file.
Wi-Fi. A wireless link shares airtime with neighbours and with every other device in the house, and its advertised rate is a ceiling, not a floor.
Old wiring. A 100 Mbps Ethernet port or a worn cable caps the whole connection at 12.5 MB/s no matter what the plan says.
The other end. A download is only as fast as the slowest server, and one source can be slower than your line by design.
Upload is usually smaller. Cable and DSL are asymmetric; fibre is often symmetric. Video calls and backups care about the upload number.
Shared peak hours. Cable segments and mobile cells are shared media, so evening speeds can sit below the daytime figure.

What each speed is actually enough for

Standard-definition streaming: about 3 Mbps per stream, roughly 0.4 MB/s.
HD streaming: about 5 Mbps, and 4K streaming about 15–25 Mbps per screen.
Video calls: 1.5–4 Mbps in each direction, which is why upload matters more here than download.
Online gaming needs very little bandwidth — 3–6 Mbps — but is ruined by latency, which speed in Mbps does not describe at all.
A 5 GB game download at 100 Mbps takes about seven minutes of steady transfer.
A 25 MB email attachment moves in about two seconds on 100 Mbps, and in about forty on 5 Mbps.

Worked examples

From the plan on the bill to the time on the clock

A 100 Mbps plan

100 Mbps ÷ 8 bits per byte = 12.5 MB/s
Allow around 8% for headers: roughly 11.5 MB/s in practice
A 5,000 MB game: 5,000 ÷ 11.5 ≈ 435 seconds

100 Mbps ≈ 12.5 MB/s, about 7 minutes for 5 GB

Your download bar shows 3 MB/s

3 MB/s × 8 = 24 Mbps of actual throughput
On a 50 Mbps plan you are using about half the line
If nothing else is downloading, the bottleneck is the far end or Wi-Fi

3 MB/s = 24 Mbps

Frequently Asked Questions

Why is my 100 Mbps connection only downloading at 12 MB/s?

Because it is not slow — it is the same speed written in a different unit. Internet plans are sold in megabits per second and download managers count megabytes per second, and a byte is eight bits, so 100 ÷ 8 = 12.5 MB/s. The couple of tenths missing from 12.5 are protocol overhead: headers and acknowledgements share the line with your file.

What is the difference between Mbps and MBps?

One letter, a factor of eight. Lowercase b means bit, uppercase B means byte, so 100 Mbps is 12.5 MBps. Providers quote Mbps, operating systems quote MB/s, and almost every argument about internet speed comes from comparing the two without converting.

How do I convert Mbps to MB/s in my head?

Divide by 8, and for a rough figure divide by 10 and add a quarter of the answer. 300 Mbps → 30 + 7.5 = 37.5 MB/s. Going the other way, multiply MB/s by 8: a download bar sitting at 5 MB/s is using 40 Mbps.

How long does a 5 GB download take on my connection?

Convert the plan to MB/s, then divide. On 100 Mbps you get 12.5 MB/s, so 5,000 MB takes about 400 seconds, or nearly seven minutes at full speed. On a 25 Mbps line the same file takes close to half an hour.

Is 1 Gbps the same as 1000 Mbps?

Yes for the line rate: gigabit per second means 1,000 megabits per second, which is 125 MB/s in file terms. In practice a single device rarely uses all of it, because one server, one Wi-Fi radio or one disk usually gives out before the connection does.

Does upload speed use the same conversion?

Yes, the factor of eight is identical in both directions. What changes is the size of the number: cable and DSL plans are asymmetric and give far less upload than download, while most fibre plans are symmetric. Video calls, cloud backups and streaming from home all depend on the upload figure.