Download Time Calculator

Line speeds count bits, file sizes count bytes, and there are 8 bits to a byte — that factor is the whole job. Both sides are decimal: 1 GB is 1,000,000,000 bytes, not 1,073,741,824. So 1 GB over 100 Mbps takes 80 seconds, not 10.

A download time is a single division, and it needs a calculator only because the two numbers going into it are quoted in different units. Connections are sold in bits per second, files are stored and displayed in bytes, and eight bits make a byte, so the rate has to be converted before the file size can be laid against it. Both sides are read decimally here, the convention data rates follow, which is why a gigabyte means a thousand million bytes. The default settings show the whole chain at once: 1 GB is 1,000,000,000 bytes, 100 Mbps is 100,000,000 ÷ 8 = 12,500,000 bytes per second, and one divided by the other is 80 seconds. What that figure describes is a line delivering its full rate from the first byte to the last with nothing else competing for it — a lower bound, not a prediction, and it says nothing about how the transfer behaves along the way. The gap between it and a real download is best read as a question about where the slowest point sits. The advertised rate is the ceiling of your own line only; a slow server, a weak Wi-Fi hop or other traffic in the house can each turn out to be the part that actually sets the pace.