Mbps vs MB/s: what’s the difference?
Learn the difference between Mbps and MB/s, how to convert correctly, and why real downloads are slower than advertised speeds.
Quick conversion: Mbps to MB/s
Internet plans and speed tests usually show megabits per second (Mbps). Downloads in apps (Chrome, Steam, Windows, macOS) often show megabytes per second (MB/s). These are not the same unit.
Example: 100 Mbps ≈ 12.5 MB/s
Why there are 8 bits in a byte
A bit is the smallest unit (0 or 1). A byte is a group of 8 bits. That’s why:
- 1 byte (B) = 8 bits (b)
- MB/s = megabytes per second
- Mbps = megabits per second
Common mistake: expecting 100 Mbps to download 100 MB each second
If your ISP sells “100 Mbps”, the theoretical maximum throughput is about 12.5 MB/s. In real life you often see less because of:
- Protocol overhead (TCP/IP, encryption)
- Wi‑Fi interference
- Server/CDN limits
- Other devices using bandwidth
Real‑world throughput: overhead and “why it’s never perfect”
Even on a perfect wired connection, a part of the bandwidth is used by headers, acknowledgements, and retransmissions. That’s normal. If you see roughly 80–95% of your plan on a good server, you’re doing fine.
Conversion table
| 25 Mbps | ≈ 3.1 MB/s |
| 50 Mbps | ≈ 6.3 MB/s |
| 100 Mbps | ≈ 12.5 MB/s |
| 200 Mbps | ≈ 25 MB/s |
| 500 Mbps | ≈ 62.5 MB/s |
| 1,000 Mbps (1 Gbps) | ≈ 125 MB/s |
MB vs MiB (and why downloads look “smaller” on some systems)
Some systems use binary units (MiB/GiB) where:
- 1 MiB = 1,048,576 bytes
- 1 MB = 1,000,000 bytes
This can make file sizes and speeds look slightly different across tools. For quick planning, the calculator uses common decimal units and gives an estimate.
Use it for planning download time
If you know your plan speed in Mbps and file size in GB, you can estimate time quickly, but it’s easier to plug the numbers into the calculator and compare scenarios (Wi‑Fi vs Ethernet, 50 vs 100 vs 500 Mbps).