Internet plans are advertised in megabits per second (Mbps), but your browser and file manager report downloads in megabytes per second (MB/s). This converter bridges the two so you can tell what download speed a quoted line rate actually delivers.
How it works
A byte is eight bits, so the two units differ by exactly a factor of eight:
MB/s = Mbps ÷ 8 · Mbps = MB/s × 8
The conversion is exact and bidirectional — type a value in either unit and the other updates instantly. Real downloads run slightly below this ceiling because of protocol overhead.
Quick reference table
A 100 Mbps broadband plan downloads at 100 ÷ 8 = 12.5 MB/s at full speed, and a 1 Gbps (1000 Mbps) line at 125 MB/s.
| Line rate (Mbps) | Download speed (MB/s) | Time to download 1 GB (approx.) |
|---|---|---|
| 25 Mbps | 3.125 MB/s | ~5 min 20 s |
| 50 Mbps | 6.25 MB/s | ~2 min 40 s |
| 100 Mbps | 12.5 MB/s | ~1 min 20 s |
| 200 Mbps | 25 MB/s | ~41 s |
| 500 Mbps | 62.5 MB/s | ~16 s |
| 1000 Mbps (1 Gbps) | 125 MB/s | ~8 s |
Download times above use 1 GB = 1,000 MB as a reference. In practice, 1 GB can mean 1,000 MB (SI) or 1,024 MB (binary GiB). The difference is small enough that it rarely matters for planning.
Why your real download speed is lower than the advertised rate
The Mbps ÷ 8 formula gives the theoretical ceiling — what you would get if 100% of the link capacity carried your file and nothing else. Real downloads are lower for several predictable reasons:
Protocol overhead. TCP/IP headers, acknowledgement packets, and TLS handshake add a small percentage to the raw bit count that your file does not benefit from. A well-tuned TCP connection on a clean link typically delivers 90–97% of theoretical throughput.
Shared infrastructure. Home broadband is usually shared at the neighbourhood node. During peak hours — evenings, weekends — contention between users drops effective throughput.
Server-side limits. The download server may rate-limit connections, or its own uplink may be saturated. A 1 Gbps line cannot help you if the server you are downloading from is only sending at 20 MB/s.
Wi-Fi overhead. A Wi-Fi connection between your device and your router adds its own overhead, interference, and half-duplex switching, often costing 20–40% of throughput on a busy household network.
A practical rule of thumb: expect 70–90% of the theoretical MB/s figure on a well-configured wired connection to a fast server, and somewhat less on Wi-Fi.
The case-sensitivity trap
Mbps (capital M, lowercase b) means megabits per second — what ISPs advertise. MB/s (capital M, capital B) means megabytes per second — what your OS shows.
Confusing the two is extremely common. A download manager showing 12.5 MB/s on a 100 Mbps connection is performing normally; it looks slower than the quoted speed only because the units differ by a factor of eight.
All maths runs locally in your browser, with nothing sent anywhere.