The One-Line Answer
1 byte = 8 bits, so Mbps ÷ 8 = MB/s.
A 100 Mbps internet connection downloads at roughly 12.5 MB/s under ideal conditions. A 1 Gbps connection maxes out at 125 MB/s.
Why Two Units Exist
The networking industry has measured speed in bits per second since the telegraph era — because networks move data one bit at a time, it's the natural unit for engineers. ISPs inherited this and still sell plans in Mbps.
Operating systems and software measure file sizes in bytes because a byte is the smallest unit a program actually works with (one character, one color value, one small number). When you see a "100 MB" file, that's 100 megabytes — 800 megabits of data.
The naming convention reinforces the split: lowercase b for bit, uppercase B for byte. So Mbps is megabits per second, MBps or MB/s is megabytes per second. One letter, 8× difference.
Conversion Table
| Plan Speed (Mbps) | Max Download (MB/s) | Real-World Download (MB/s)* |
|---|---|---|
| 10 Mbps | 1.25 MB/s | ~1.0-1.1 MB/s |
| 25 Mbps | 3.1 MB/s | ~2.5-2.8 MB/s |
| 50 Mbps | 6.25 MB/s | ~5-5.6 MB/s |
| 100 Mbps | 12.5 MB/s | ~10-11 MB/s |
| 200 Mbps | 25 MB/s | ~20-22 MB/s |
| 300 Mbps | 37.5 MB/s | ~30-34 MB/s |
| 500 Mbps | 62.5 MB/s | ~50-56 MB/s |
| 1 Gbps (1000 Mbps) | 125 MB/s | ~100-115 MB/s |
| 2 Gbps | 250 MB/s | ~200-230 MB/s |
*Real-world downloads hit 80-92% of the math because of TCP/IP protocol overhead, TLS encryption, and the server's own upload speed. A single download rarely hits the full theoretical maximum even on a perfect connection.
How Long to Download Common Files
| File | Size | @ 50 Mbps | @ 300 Mbps | @ 1 Gbps |
|---|---|---|---|---|
| Music album (MP3) | 100 MB | 18 seconds | 3 seconds | <1 second |
| 4K movie | 20 GB | 1 hour | 10 minutes | 3 minutes |
| AAA game | 100 GB | 5 hours | 50 minutes | 15 minutes |
| OS image | 6 GB | 18 minutes | 3 minutes | 1 minute |
| Operating system update | 2 GB | 6 minutes | 1 minute | 20 seconds |
These are best-case. Real downloads depend heavily on the server, your Wi-Fi, and background activity.
Why Your Download Speed Looks Lower Than Your Plan
Beyond the Mbps-vs-MBps conversion, a few more things eat into the visible number:
- Protocol overhead — TCP/IP, TLS, and HTTP/2 headers consume 3-10% of raw bandwidth
- Server limits — the server's upload speed or per-connection cap may be below your connection capacity
- Wi-Fi — wireless routinely delivers 40-80% of a wired connection
- Concurrent traffic — streaming, backups, and other devices are all sharing the pipe
- CDN location — downloading from a far-away server adds latency that drags throughput
If your speed test hits plan speed but your actual downloads are slow, see speed test good but internet slow.
What About Gigabytes and Gigabits?
Same rule, bigger unit. 1 Gbps = 1000 Mbps = 125 MB/s = 0.125 GB/s. When a storage drive is rated at "6 Gbps" (like SATA III), that's 6 gigabits per second — roughly 750 MB/s, which matches what SSDs deliver.
Cheat Sheet
- Divide by 8 to go from Mbps to MB/s
- Multiply by 8 to go from MB/s to Mbps
- Lowercase b = bit, Uppercase B = byte
- ISPs sell in Mbps, OSes report in MB/s — neither is wrong
- Plan speed in Mbps × 0.09 ≈ realistic download MB/s on a wired connection
Frequently Asked Questions
Is Mbps the same as MB/s?
No. Mbps (megabits per second) is 8× smaller than MB/s (megabytes per second). A 100 Mbps connection downloads at about 12.5 MB/s maximum.
Why do ISPs advertise in Mbps instead of MB/s?
Networking has measured speed in bits since its origin — bits are the natural unit for data transmission. Using Mbps also makes the numbers look 8× larger in marketing.
How do I convert Mbps to MB/s?
Divide Mbps by 8. A 300 Mbps plan delivers up to 37.5 MB/s; real-world downloads typically hit 30-34 MB/s after protocol overhead.