Data Transfer Time Calculator

Divide the file size (converted to bits) by the connection speed (in bits per second). Since one byte is eight bits, a file size in megabytes is multiplied by 8 to compare it against a speed in megabits per second. For example, a 1,000 MB file over a 100 Mbps link takes 1,000 x 8 / 100 = 80 seconds at the nominal rate.

Internet providers advertise speed in bits per second (Mbps, Gbps), while operating systems and file managers report file sizes in bytes (MB, GB), and one byte equals eight bits. That factor of 8 is why a '100 Mbps' connection downloads at most about 12.5 MB per second. This calculator keeps the units straight, so a lowercase b means bits and an uppercase B means bytes.

Real transfers never reach the full advertised speed because some bandwidth carries protocol headers, retransmitted packets, and encryption instead of your file. The overhead percentage reduces the effective throughput by that share, so 20% overhead means only 80% of the nominal rate moves payload. A common rule of thumb for TCP over Ethernet is roughly 8 to 12% overhead; leave it at 0 for the theoretical best case.

MB (megabyte) is the decimal unit and equals 1,000,000 bytes, which is how drive makers and most file managers label sizes. MiB (mebibyte) is the binary unit and equals 1,048,576 bytes (1,024 x 1,024), which is how RAM and many operating system readouts actually count. The calculator offers both so your file size matches whatever source you copied it from.

This tool assumes your connection sustains the speed you enter, but real throughput is limited by the slowest link in the path, server limits, disk read and write speed, Wi-Fi interference, and network congestion. Treat the result as a best-case planning number and add protocol overhead to get closer to what you will actually see.

It uses whatever single speed you enter, so pick the direction that matters: your download speed for receiving a file, or your upload speed for sending one. Home connections are often asymmetric, with upload much slower than download, so use the correct figure for an accurate estimate.