Download Time Calculator
How long a file takes to download at a given connection speed.
Leave at 100% to take the speed at face value. Real transfers usually sustain 80–90% of an advertised line once protocol overhead and the far-end server are accounted for.
Download time
6 min 40 s
How it works
Both sides of the sum are converted to bits, divided, and turned back into days, hours, minutes and seconds. That conversion is the whole point: broadband is sold in megabits per second while files are measured in megabytes, and one byte is eight bits — so a 100 Mbps line moves about 12.5 MB every second, not 100. Set speed actually achieved below 100% to allow for the gap between an advertised line and a real transfer.
time (s) = size in bits ÷ (speed in bits/s × efficiency)Example
- 5 GB at 100 Mbps = 6 min 40 s
- 700 MB at 10 Mbps = 9 min 20 s
- 25 GB at 1 Gbps = 3 min 20 s
A best case. Server limits, Wi-Fi, congestion and a shared line all cost time this arithmetic can't see, so treat the result as the floor rather than a promise.
About this calculator
Enter a file size and a connection speed and this gives the transfer time in days, hours, minutes and seconds. The units on both sides can be set independently — a 4.7 GB file over a 100 Mbps line, or 850 MiB at 2.5 MB/s — because the mismatch between how files are measured and how connections are sold is exactly where this calculation goes wrong by hand.
Broadband is advertised in megabits per second and files are stored in megabytes, and a byte is eight bits, so a 100 Mbps line carries about 12.5 MB each second. The calculator converts both sides to bits before dividing, and shows the effective speed in MB/s alongside the answer so the working is visible. It applies equally to uploads — the arithmetic doesn't care which direction the file is moving.
Frequently asked questions
How do I calculate download time?
Divide the file size by the transfer speed, with both in the same unit. Convert the file to bits (multiply bytes by 8) and the speed to bits per second, then divide: a 5 GB file is 40,000,000,000 bits, and over a 100 Mbps line that is 400 seconds, or 6 minutes 40 seconds.
Why is my 100 Mbps connection not downloading 100 MB per second?
Because Mbps is megabits per second and file sizes are in megabytes, and one byte is eight bits. A 100 Mbps line moves at most 100 ÷ 8 = 12.5 MB per second. The lowercase b in Mbps means bits; the uppercase B in MB/s means bytes.
How long does it take to download a 1 GB file?
At 10 Mbps roughly 13 minutes 20 seconds, at 100 Mbps about 80 seconds, and at 1 Gbps about 8 seconds. Enter 1 and GB with your own speed to get the exact figure — the calculator shows the seconds as well as the rounded breakdown.
What is the difference between MB and MiB?
A megabyte (MB) is 1,000,000 bytes and a mebibyte (MiB) is 1,048,576 — about 4.9% more. Storage and networking quote MB and GB, while operating systems usually report the binary sizes, sometimes labelling them MB anyway. Both are in the unit list, so you can enter the size exactly as it was shown to you.
Why is my real download slower than the calculated time?
The calculation is a best case: it assumes the full line speed is available for the whole transfer. In practice protocol overhead, the server at the other end, Wi-Fi, and anyone else sharing the connection all take a share. Setting 'speed actually achieved' to 80–90% gives a more realistic figure than the raw line speed.
Can I use this for upload time?
Yes. Enter your upload speed instead of your download speed — the arithmetic is identical. Just remember that most home connections upload far more slowly than they download, so use the upload figure from a speed test rather than the number on your plan.