Networking · Speed & Units
Data Transfer Rate Converter
Convert a data speed between bits per second (Mbps, Gbps), bytes per second (MB/s, GB/s) and the binary units (MiB/s, GiB/s, Mibps) that download managers and Windows quietly use. It shows every step of the arithmetic, the speed in all 16 units at once, and how long 1 GB, 10 GB or your own file takes at that speed, so you can see why a 100 Mbps plan downloads at about 12 MB/s.
Also listed inData & Storage
Your inputs
Quick start — try a typical case
The speed you want to convert, in the unit picked beside it. Example: for a "100 Mbps" broadband plan enter 100 and pick Mbps; for a download showing 5 MB/s enter 5 and pick MB/s.
The unit you want. Units with an "i" (KiB/s, MiB/s, GiB/s, Mibps) are binary: 1 MiB = 1,048,576 bytes, not 1,000,000. Windows and many download tools use these but label them "MB", so 100 Mbps shows as 11.9 there instead of 12.5.
A file to time at this speed, e.g. 50 GB for a game or 4 GB for an HD film. Leave it blank or 0 to skip. The time is theoretical: the full line speed with no protocol overhead or slow servers.
Your result Live
100 Mbps =
12.5 MB/s
100 Mbps × 10⁶ ÷ 8 ÷ 10⁶ = 12.5 MB/s
- In bits per second
- 100,000,000 bps
- 1 Mbps =
- 0.125 MB/s
- Time for 1 GB
- 1 min 20 s
- Time for 10 GB
- 13 min 20 s
- Time for 50 GB
- 1 h 6 min 40 s
- Data moved in 1 hour
- 45 GB
Working
Every unit is turned into bits per second first, then into the unit you want. 1 byte = 8 bits; decimal prefixes are powers of 10, binary ones (Ki, Mi, Gi) are powers of 2.
1: Step 1 · Mbps to bits per second
100 × 10⁶
Expression becomes 100,000,000 bps
2: Step 2 · Bits per second to MB/s
100,000,000 ÷ 8 ÷ 10⁶
Expression becomes 12.5 MB/s
3: Step 3 · Time for 50 GB
50,000,000,000 bytes × 8 ÷ 100,000,000 bps
Expression becomes 4,000 s = 1 h 6 min 40 s
Answer: 100 Mbps = 12.5 MB/s
100 Mbps in every unit
16 rowsBits vs bytes: you converted between bits (b) and bytes (B), which is a factor of 8. Internet plans are sold in Mbps but downloads show MB/s, so divide the plan speed by 8: 100 Mbps is 12.5 MB/s at best.
Two classic traps. (1) Bits vs bytes: b is bits, B is bytes, and 1 byte = 8 bits, so a 100 Mbps plan moves at most 12.5 MB/s. (2) Decimal vs binary: 1 MB = 1,000,000 bytes but 1 MiB = 1,048,576 bytes, so the same 100 Mbps shows as about 11.9 in a tool that counts in MiB/s.
Transfer times here are theoretical: the full line speed with no overhead. Real downloads lose about 5–15 % to TCP/IP, Wi-Fi and encryption, and are often limited by the server. Use the Download Time & Bandwidth Calculator to model overhead.
Network speeds always use decimal prefixes: 1 Gbps Ethernet is exactly 1,000,000,000 bits per second, never 2³⁰.
How this is calculated
Result = value × f(from) ÷ f(to) · f = bits per second in one unit: Mbps = 10⁶, MB/s = 8 × 10⁶, MiB/s = 8 × 2²⁰ · Time = file size (bytes) × 8 ÷ speed (bits/s)
- b / B
- Small b = bit, capital B = byte; 1 B = 8 b
- K, M, G, T
- Decimal (SI) prefixes: 10³, 10⁶, 10⁹, 10¹²
- Ki, Mi, Gi
- Binary (IEC) prefixes: 2¹⁰ = 1,024, 2²⁰ = 1,048,576, 2³⁰ = 1,073,741,824
- f(unit)
- How many bits per second one of that unit is
Every speed is first turned into plain bits per second, then divided by the size of the unit you want. Bytes are 8 bits, so going from Mbps to MB/s divides by 8; decimal prefixes (K, M, G) step by 1,000 while binary ones (Ki, Mi, Gi) step by 1,024. That is why a 100 Mbps broadband plan shows about 12.5 MB/s in a browser and about 11.9 in a tool that counts in MiB/s, and neither means the line is slow.
Assumptions & sources
- Decimal prefixes follow the SI (1 k = 1,000) and binary prefixes follow IEC 80000-13 (1 Ki = 1,024); 1 byte = 8 bits.
- Transfer times assume the full stated speed for the whole transfer, with no protocol overhead, latency or server limits.
- Speeds are treated as exact; a plan's advertised speed is usually a maximum, not a guarantee.
- 1Prefixes for binary multiples (kibi, mebi, gibi; IEC 60027-2 / IEC 80000-13) — NIST
- 2SI prefixes (kilo, mega, giga, tera) — NIST
- 3The International System of Units (SI Brochure) — decimal prefixes — BIPM
- 4IEC 80000-13:2008 Quantities and units — Part 13: Information science and technology (bit, byte, binary prefixes) — IEC
Calculator ID NET-RATE-001 · version 1.0.0
Common questions
Why does my 100 Mbps plan only download at about 12 MB/s?
Because plans are sold in megabits per second and download managers show megabytes per second. A byte is 8 bits, so 100 Mbps ÷ 8 = 12.5 MB/s at best. After 5–15 % protocol overhead, 10.5–12 MB/s is normal and means the line is working properly.
What is the difference between MB/s and MiB/s?
MB/s counts 1,000,000 bytes a second; MiB/s counts 1,048,576 bytes a second. So 12.5 MB/s is the same speed as 11.92 MiB/s. Windows, Steam and many download tools use MiB but print "MB", which makes speeds look about 5 % lower.
How many MB/s is 1 Gbps fibre?
1 Gbps = 1,000 Mbps = 125 MB/s (about 119 MiB/s). In practice you will see roughly 110–118 MB/s over a good wired connection; Wi-Fi is usually slower.
How long does 10 GB take at 100 Mbps?
10 GB = 80,000,000,000 bits. Divided by 100,000,000 bits a second, that is 800 seconds, or 13 min 20 s, in theory. With 10 % overhead expect nearer 15 minutes.
Is Kbps 1,000 or 1,024 bits per second?
1,000. Network and telecom speeds always use decimal prefixes, so 1 Kbps = 1,000 bps and 1 Mbps = 1,000,000 bps. The binary unit is written Kibps (1,024 bps) and is rare outside some software tools.