Internet speeds are measured in bits per second, files in bytes, and a byte is 8 bits: that is the whole trick. At 300 Mbps you can move at most 300 ÷ 8 = 37.5 MB a second, so a 50 GB download takes at least 50,000 ÷ 37.5 = 1,333 seconds – 22 minutes, or about 25 minutes at the 90% of the speed most connections really deliver. Type the file size and your speed in the units you have, and the calculator gives the time, the speed in MB/s and how much you move in a minute and an hour.
Download times at the full speed
| File size | 25 Mbps | 100 Mbps | 300 Mbps | 1 Gbps |
|---|---|---|---|---|
| 1 GB | 5 min 20 s | 1 min 20 s | 27 s | 8 s |
| 5 GB | 26 min 40 s | 6 min 40 s | 2 min 13 s | 40 s |
| 25 GB | 2 h 13 min | 33 min 20 s | 11 min 7 s | 3 min 20 s |
| 50 GB | 4 h 26 min | 1 h 6 min | 22 min 13 s | 6 min 40 s |
| 100 GB | 8 h 53 min | 2 h 13 min | 44 min 27 s | 13 min 20 s |
Each step up in speed cuts the time in proportion: four times the speed, a quarter of the time. Above about 1 Gbps, the bottleneck is often the server, the Wi-Fi or the disk rather than the line.
Bits and bytes, MB and MiB
| Written | Means | In bytes |
|---|---|---|
| 1 Mbps | 1 million bits per second | 125,000 bytes per second |
| 1 MB/s | 1 million bytes per second | = 8 Mbps |
| 1 GB | 1,000 MB | 1,000,000,000 |
| 1 GiB | 1,024 MiB | 1,073,741,824 |
Download apps and game stores usually show MB/s; providers sell Mbps. If your computer reports sizes in GiB but calls them GB, pick GiB in the calculator for the exact figure.
Getting a realistic estimate
Run a speed test on the device you will use, close to the router or on a cable, and compare it with your plan: that share is what to type. Downloads from a busy server can be slower still, whatever your line.
Once zet4u is saved, this calculator works offline – useful exactly when the connection is the problem.
Frequently asked questions
How long does it take to download 50 GB at 300 Mbps?
At the full 300 Mbps, 50 × 8,000 ÷ 300 = 1,333 seconds, about 22 minutes. At 90% of the speed, which is closer to real life, about 25 minutes.
How do I convert Mbps to MB per second?
Divide by 8, because a byte has 8 bits. 100 Mbps is 12.5 MB/s; 1 Gbps (1,000 Mbps) is 125 MB/s.
Why is my download slower than my plan's speed?
Wi-Fi signal, other devices on the network, a busy evening and the server at the other end all cut it. Run a speed test and type the share you really get.
What is the difference between GB and GiB?
A GB is 1,000,000,000 bytes, the way storage makers and download stores count; a GiB is 1,073,741,824 bytes (1,024³), the unit some operating systems show while calling it GB. A 50 GiB file is about 53.7 GB.
Is upload time worked out the same way?
Yes, with your upload speed. On many cable and DSL plans upload is far slower than download, so a big backup can take several times longer than downloading the same amount.
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