Enter a file size and time.
Speed & transfer
Download Speed Calculator
Find your average download speed from a file size and the time it took.
What is a download speed calculator?
This tool works backwards from something you already know: how big a file was and how long it took to download. It returns the average speed in megabits per second (Mbps) and megabytes per second (MB/s), so you can compare a real download with the speed on your internet plan.
The formula
Speed (Mbps) = file size in MB × 8 ÷ time in seconds. Multiplying by 8 converts megabytes into megabits, which is the unit providers use. Divide the answer by 8 again to see the MB/s figure that browsers and download managers display.
Example
A 500 MB file that finishes in 45 seconds averages 500 × 8 ÷ 45 ≈ 88.9 Mbps, or about 11.1 MB/s.
Why the result can be lower than your plan
Advertised speeds are usually maximums. Wi-Fi loss, server limits, other people on the network and protocol overhead all reduce the average. If a very large file from a fast server still downloads far below your plan, test over Ethernet to see whether the router or the provider is the limit.
FAQ
Frequently asked questions about the Download Speed Calculator
How do I convert MB/s to Mbps?
Multiply MB/s by 8. A download running at 10 MB/s is moving about 80 Mbps of data.
Why is my download slower than the speed I pay for?
Plans list a best-case figure. Wi-Fi conditions, the server you download from, congestion and overhead can all lower the average you actually see.
Should I use MB or Mb for file size?
Use megabytes (MB), which is what file managers show. The calculator converts to megabits for you.
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Use this toolResults are estimates for planning. Last reviewed 20 September 2026.