Download time calculator
How long a file takes to transfer at a given speed — and why it is always a little longer than the arithmetic says. Also converts between the bits providers sell and the bytes download dialogs show.
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The arithmetic
Time = size in bits ÷ speed in bits per second. A 5 GB file is 40,000 megabits; at 100 Mbps that is 400 seconds, or 6 minutes 40 seconds — and closer to 7½ minutes in practice.
To see what your own line delivers, run the speed test and bring the download figure here.
Why is Mbps different from MB/s?
Providers sell speed in megabits per second; download dialogs show megabytes per second. A byte is eight bits, so 100 Mbps moves at most 12.5 MB/s.
Why does a download take longer than this?
Every packet carries headers, encryption adds a little, and acknowledgements travel the other way, so about 90–95 % of the line rate carries the file. Beyond that, the server, Wi-Fi and other traffic on the line all take a share.
What is the difference between GB and GiB?
A GB is 1,000,000,000 bytes; a GiB is 1,073,741,824. Disk makers and most apps use GB; Windows shows GiB but labels it GB — which is why a “1 TB” drive appears as about 931 GB there.
Is anything I type sent anywhere?
No. The calculation runs in your browser.