How to use the download & upload time calculator
The formula
Time = file size in megabits ÷ speed in Mbps. File sizes are converted first: 1 GB = 1,000 MB, and every byte is 8 bits, so 1 GB = 8,000 megabits. Divide by your line speed to get seconds.
Which speed should you enter?
Use the speed you actually measure (run a speed test), not the headline speed on the box. And note the direction: on most home broadband, uploads are far slower than downloads — a 1 GB video can upload ten times slower than it downloaded.
Example
A 1 GB file at 100 Mbps takes about 80 seconds. 1 GB = 8,000 megabits; 8,000 ÷ 100 = 80 s. At a typical UK/US entry-level 36 Mbps, the same file takes about 3 minutes 42 seconds.
Frequently asked questions
Why is my real download slower than the estimate?
The calculator gives the theoretical time on a perfect connection. Protocol overhead, Wi-Fi quality, other devices, and the server at the other end typically add around 10% or more.
Why do I enter speed in Mbps but file size in GB?
Because that is how the industry sells them: line speeds are measured in megabits per second (Mbps), while files are measured in bytes (MB, GB). There are 8 bits in a byte, which is why a 100 Mbps line downloads at most 12.5 MB per second.
Does upload use the same maths?
Yes — pick Upload and use your upload speed (often much lower than download speed on UK and US home broadband).
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