What is MB/s?
MB/s stands for megabytes per second: one million bytes, or 8 million bits, every second. You see it wherever software moves files, in download managers, file-copy windows and drive specifications, and 1 MB/s equals 8 Mbps.
The definition
A megabyte is 1,000,000 bytes and a byte is 8 bits, so:
1 MB/s = 1,000,000 B/s = 8,000,000 bit/s = 8 Mbps 1 kB/s = 1,000 B/s = 8 kbps 1 GB/s = 1,000 MB/s = 8 Gbps
It is sometimes written MBps or MB/sec. The capital B is what matters: MB/s is bytes, Mbps is bits. Network speeds and plans use Mbps, explained in what is Mbps.
Where you see MB/s
- Downloads. Browsers, game launchers and download managers report how quickly the file grows on disk, in kB/s or MB/s.
- File copies. Copying to a USB stick, an external drive or a network share shows a speed in MB/s in most operating systems.
- Drive and memory card specs. Read and write speeds for SSDs, hard drives and cards are quoted in MB/s, because storage is measured in bytes.
- Cloud sync and backup apps. Many show upload progress in MB/s, even though your plan's upload is sold in Mbps.
Small rates appear as kB/s: 500 kB/s is 4 Mbps, which is why a slow download that "only" shows a few hundred kB/s may still be using a modest plan fully. The kB/s to Mbps converter covers that range.
Port and cable speeds in MB/s
Connections such as USB and Ethernet are rated in bits per second. Dividing by 8 gives the ceiling in MB/s. These are nominal signalling rates; real copies are lower because of encoding, protocol overhead and the drive at each end.
| Connection | Nominal rate | Ceiling in MB/s |
|---|---|---|
| USB 2.0 | 480 Mbps | 60 MB/s |
| Gigabit Ethernet | 1 Gbps | 125 MB/s |
| 2.5GBASE-T Ethernet | 2.5 Gbps | 312.5 MB/s |
| USB 3.2 Gen 1 | 5 Gbps | 625 MB/s |
| USB 3.2 Gen 2 | 10 Gbps | 1,250 MB/s |
| 10GBASE-T Ethernet | 10 Gbps | 1,250 MB/s |
| Thunderbolt 3/4 | 40 Gbps | 5,000 MB/s |
A copy is limited by the slowest part of the chain. A fast SSD on a USB 2.0 port cannot exceed 60 MB/s, and a gigabit network share cannot exceed 125 MB/s however fast the drives are. The file transfer time calculator has these connections as presets.
MB/s vs MiB/s
Some programs count in binary units: 1 MiB/s is 1,048,576 bytes per second, about 4.9% more than 1 MB/s. Some label it MiB/s; others still write "MB/s" while dividing by 1,024 × 1,024. The difference is small for a quick check but adds up in precise comparisons:
1 MB/s = 8 Mbps 1 MiB/s = 8.388608 Mbps 117.5 MB/s ≈ 112.1 MiB/s
If a program's reading and a speed test disagree by about 5%, binary units are a likely reason.
The same applies to sizes. A file listed as "4 GB" by software that counts in binary is 4 GiB, which is 4,294,967,296 bytes. Copying it at 100 MB/s takes about 42.9 seconds, not 40. For a quick estimate the difference rarely matters; for comparing two tools, or a tool with a speed test, it can explain the whole gap.
Using MB/s to estimate time
Because file sizes and MB/s are both in bytes, time is a simple division with no factor of 8:
seconds = size in MB ÷ MB/s 10 GB at 100 MB/s = 10,000 MB ÷ 100 = 100 s
When the speed is a plan in Mbps, convert first: a 500 Mbps plan is at most 62.5 MB/s, so the same 10 GB takes at least 160 seconds. The download time calculator accepts either unit and does the conversion for you, and the MB/s to Mbps converter handles single values.
Key takeaways
- MB/s is megabytes per second: 1 MB/s = 8 Mbps.
- You see it in downloads, file copies, drive specs and backup apps; plans use Mbps.
- Port ratings are in bits: divide by 8 for the MB/s ceiling (gigabit Ethernet = 125 MB/s).
- MiB/s is binary: 1 MiB/s = 8.388608 Mbps, about 5% more than 1 MB/s.
Frequently asked questions
How many Mbps is 1 MB/s?
8 Mbps. Multiply any MB/s figure by 8 to get Mbps: 25 MB/s is 200 Mbps.
Is 100 MB/s fast?
For a download it is 800 Mbps, which needs a plan of about 1 Gbps. For a file copy it is typical of external hard drives and well below what USB 3.2 or a good SSD can reach.