Download Time Estimator
Estimate download time from a file size and connection speed, with bits and bytes kept straight.
About this tool
Enter a file size and a connection speed and this updates live with an estimated download time. The single most common mistake in tools like this is mixing up bits and bytes — internet connection speeds are conventionally advertised in bits per second (Mbps, Gbps), while file sizes are reported in bytes (MB, GB). There are 8 bits in a byte, so a "100 Mbps" connection downloads at a theoretical maximum of 12.5 MB/s, not 100 MB/s. This tool's speed dropdown clearly separates the two conventions so you don't have to do that conversion in your head.
For the actual maths: file size is converted using the binary (1024-based) convention — 1 MB = 1,048,576 bytes — since that's how operating systems typically report file sizes. Connection speed is converted using the decimal (1000-based) convention — 1 Mbps = 1,000,000 bits/sec — since that's the standard way network/ISP speeds are quoted. Both are then expressed in bits and divided to get seconds.
This is a theoretical best case assuming the full advertised speed is sustained with no overhead, contention, or slow server-side throttling — real-world downloads are usually somewhat slower than this estimate.