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Mbps vs MB/s: Why Your Download Speed Is Not Your Internet Speed

Updated · 2 min read

You pay for 500 Mbps but your download window shows 55. Is your provider cheating you? Almost certainly not: the two numbers use different units. Once you know how to convert them, you can tell whether a connection is working properly.

Bits vs bytes

Network speeds are measured in bits per second, written Mbps (megabits per second) with a lowercase “b”. File sizes and transfer speeds are measured in bytes, written MB/s with a capital “B”. A byte is eight bits, so you divide Mbps by 8 to get MB/s.

Advertised speed Maximum download
25 Mbps 3.1 MB/s
100 Mbps 12.5 MB/s
300 Mbps 37.5 MB/s
500 Mbps 62.5 MB/s
1 Gbps (1,000 Mbps) 125 MB/s

The megabits per second to megabytes per second converter does the maths for any speed, and the reverse converter turns a download figure back into a line speed.

Estimating a download time

Divide the file size in megabytes by the speed in MB/s. A 50 GB game is 50,000 MB. On a 100 Mbps line (12.5 MB/s) that takes 4,000 seconds, or about 67 minutes. On a gigabit line (125 MB/s) it takes about 400 seconds, or 6 to 7 minutes. Real downloads are usually 10 to 20 percent slower than the maximum because of protocol overhead.

How much speed do you need?

  • Web browsing and email: 5 to 10 Mbps.
  • HD video streaming: about 5 to 8 Mbps per stream.
  • 4K streaming: about 15 to 25 Mbps per stream.
  • Video calls: 3 to 8 Mbps up and down.
  • Online gaming: 10 to 25 Mbps is enough, but latency matters more than speed.
  • A busy household: add up what each person might use at the same time. 200 to 500 Mbps covers most families.

Why you may not get the advertised speed

  • Wi-Fi: distance, walls and interference can cut speeds in half or more. Test with a wired connection to see the true line speed.
  • Server limits: the website or service you download from may not be able to send data as fast as you can receive it.
  • Shared connections: other devices on your network share the same line.
  • Upload vs download: many plans have much lower upload speeds than download speeds.

If a wired speed test on your computer shows close to the plan speed, your line is fine and any slowness comes from Wi-Fi or the remote server.

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