How long will that download take?
Enter a file size and your connection speed to see the download time in hours, minutes and seconds. Bits and bytes are handled correctly, and a real-world overhead slider keeps the estimate honest.
Your numbers
What this means
This file at common speeds
| Speed | Effective MB/s | At full speed | With overhead |
|---|
How download time works
Bits, bytes and why the math trips people up
Internet plans are sold in bits per second (Mbps means megabits), but files are measured in bytes (MB means megabytes). There are 8 bits in a byte, so a 100 Mbps line moves only about 12.5 megabytes each second. The calculator converts your file size to bits, divides by the line speed, and gives the time. That single factor of 8 is the reason a download feels slower than the headline number suggests.
Units here are decimal, the 1000-based kind marketers use: 1 KB is 1,000 bytes, 1 MB is 1,000,000 bytes, 1 GB is 1,000,000,000 bytes. Your operating system often shows the binary sizes instead (1 MiB is 1,048,576 bytes), which is why a file can look a few percent bigger on disk than the download claimed.
Why real downloads run slower than the theory
The theoretical time assumes every bit of your line carries file data at full speed, all the time. Reality is messier. Protocol overhead, TCP acknowledgements, Wi-Fi retransmissions, a busy server and network congestion all shave off throughput. The overhead field trims your effective speed so the estimate lands closer to what you will actually see, effective speed being the line speed times one minus the overhead percent. Ten percent is a sensible default for a healthy connection, and you can raise it for flaky Wi-Fi or a slow source.
Common questions
Why does a 100 Mbps connection not download 100 MB per second?
Because speed is measured in bits and files in bytes, and 1 byte equals 8 bits. A 100 Mbps line carries 100 megabits per second, which is only about 12.5 megabytes per second before any overhead. Divide the advertised megabit speed by 8 to get the rough megabytes-per-second figure.
What should I put for overhead?
Ten percent is a good starting point for a solid wired or strong Wi-Fi connection. If you are on weak Wi-Fi, a congested network or downloading from a slow server, try 20 to 30 percent. Overhead simply reduces the effective speed so the time estimate reflects the real world rather than the ideal.
Are KB, MB and GB counted as 1000 or 1024?
This tool uses decimal units, so 1 MB is 1,000,000 bytes, the way internet providers and file sizes are usually advertised. Operating systems often report binary sizes (1 MiB is 1,048,576 bytes), which makes files look about 5 to 7 percent larger on disk.
Does the calculator handle upload time too?
Yes. Download and upload use the same math: file size divided by the connection speed. Just enter your upload speed in the connection speed field and read the result as upload time.
Why is my real download slower than the estimate?
The theoretical figure assumes the whole line is dedicated to your file at full speed. Shared bandwidth, server caps, distance to the source, Wi-Fi interference and protocol overhead all reduce throughput. Raise the overhead percent to bring the estimate closer to what you observe.
How do I convert Mbps to MB per second by hand?
Divide the megabit speed by 8. So 50 Mbps is about 6.25 MB per second, 200 Mbps is about 25 MB per second, and 1 Gbps (1000 Mbps) is about 125 MB per second, all before overhead.
Estimates only. Real download times vary with congestion, server limits, Wi-Fi and protocol overhead. Sizes and speeds use decimal (1000-based) units.