Estimate how long a file takes at a given connection speed.
How much of the rated speed a real transfer achieves. 85% is typical on a wired connection.
About 7.8 min at 100 Mbps
The arithmetic assumes the connection is the bottleneck, and often it is not. A single download can be limited by the server, by a slow disk at your end, or by the size of the TCP window on a long path, and none of those improve when you buy a faster line. On Wi-Fi, the link to the router usually decides the outcome long before the internet connection does. Treat this as the floor on time rather than the expected time.
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