Download time calculator

Enter the size of the file and the speed of your connection. The tool gives the time, with an allowance for overhead.

How the time is worked out

Time = file size in bits divided by the usable speed in bits per second. The tool converts the size to bits, multiplies the connection speed by the share of it that you expect to use (the "usable share"), and divides. A share of 100% gives the best case; 80 to 90% is a fair guess on a wired connection.

An example

A 4.7 GB file on a 100 Mbit/s line: 4.7 GB is 4.7 x 10^9 bytes, which is 37.6 x 10^9 bits. At 100 x 10^6 bit/s that is 376 seconds in the best case, about 6 minutes 16 seconds. At 80% of the speed it is 470 seconds, about 7 minutes 50 seconds. Type the numbers into the tool above to check.

Things that change the real time

• Wi-Fi or a cable. Cables are steadier.
• Other users and devices on the connection.
• The server's speed and the distance to it.
• Throttling. Some providers slow heavy transfers after a data limit, and servers sometimes limit each user.
• Resuming. If a download breaks and restarts, add that time.

Upload takes longer

Many home connections upload much slower than they download. Use your upload speed in the tool when you send files.

Tip for big files

For a large download, use a wired connection, pause other downloads, and avoid the busiest hour of the evening.

Common mistakes

1. Using MB/s as if it were Mbit/s: divide Mbit/s by 8 first (or choose the right unit in the tool).
2. Mixing GB and GiB for the file size. A "4 GB" download is usually decimal.
3. Ignoring the allowance for overhead.

This is an independent guide. It is not connected with the IERS, BIPM, IANA, NIST or any company named here. Facts were read on 14 November 2026 from the sources named on each page; calculated values come from Python.