Download Time Calculator
Enter the file size and your connection speed to get the download time in hours, minutes and seconds. The overhead percentage allows for protocol overhead and a connection that rarely runs at its advertised speed.
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Formula
bits = file size x bytes per unit x 8
effective speed = speed (bits/s) x (1 - overhead / 100)
time (s) = bits / effective speed
Units are decimal: 1 KB = 1,000 B, 1 GB = 1,000,000,000 B. 1 MB/s = 8 Mbps. The result is rounded to whole seconds and split into hours, minutes and seconds.
Worked example
A 1 GB file on a 100 Mbps connection with 10% overhead:
- bits = 1 x 1,000,000,000 x 8 = 8,000,000,000
- effective speed = 100 x 0.9 = 90 Mbps = 90,000,000 bits/s
- time = 8,000,000,000 / 90,000,000 = 88.9 s, shown as 89 seconds (0 h 1 m 29 s)
A 50 GB file at 25 MB/s with no overhead takes 50,000,000,000 / 25,000,000 = 2,000 s, which is 33 m 20 s.
Frequently asked questions
How do I calculate download time?
Convert the file size to bits (bytes x 8) and divide by the speed in bits per second. A 1 GB file is 8,000,000,000 bits, so at 100 Mbps with no overhead it takes 80 seconds.
What is the difference between Mbps and MB/s?
Mbps is megabits per second and MB/s is megabytes per second. One byte is 8 bits, so 100 Mbps equals 12.5 MB/s. Internet plans are sold in Mbps, while download managers usually show MB/s.
Why is my real download slower than the calculation?
Protocol headers, Wi-Fi quality, server limits and other devices on the network all take a share. An overhead of 10% turns 100 Mbps into 90 Mbps, so 1 GB takes about 89 seconds instead of 80.
Does this use 1000 or 1024 for a kilobyte?
It uses decimal prefixes: 1 KB is 1000 bytes and 1 GB is 1,000,000,000 bytes, which matches how network speeds and drive makers count. Operating systems that count in 1024s will show the same file as a smaller number at the GB level: a 1 GB (1,000,000,000 byte) file appears as about 0.93 GB.