Download Time Calculator

This is the theoretical best case — the raw file size divided by the raw link speed. In practice transfers are slower because of TCP/IP and TLS overhead, the latency of each round trip, packet loss and retransmissions, server-side throttling, and other traffic sharing the link. A useful rule of thumb is to expect roughly 10–20% less than the theoretical figure on a clean connection, and more on a congested or high-latency one.

It trips up almost everyone: file sizes are measured in bytes (KB, MB, GB) while connection speeds are sold in bits per second (Kbps, Mbps, Gbps), and one byte is eight bits. So a 100 Mbps line moves at most about 12.5 MB per second, not 100. This calculator does the ÷8 conversion for you, so you can enter the file in the units you see on disk and the speed in the units your ISP advertises.

Transfer time is part of how fast your site feels: large, unoptimised assets stretch page-load times, especially on mobile connections. Use this to sanity-check asset and backup sizes, then let Uptimeify track your real-world response times continuously and alert you when pages start loading slowly for actual visitors.