Network throughput calculator
Enter how much data moved and how long it took to get the actual throughput in every rate unit. Add the link speed to see what percentage of the link the transfer used.
Runs entirely in your browser. Nothing you type is sent anywhere.
How throughput is calculated
Throughput is what a transfer actually achieved, as opposed to the rated speed of the link. It is the data divided by the elapsed time:
throughput (Mbps) = data in MB × 8 ÷ seconds utilisation = throughput ÷ link speed × 100%
The calculator converts the result into every unit, from bps to Gbps and from B/s to GB/s, plus MiB/s, so you can compare it with a speed test, a plan or a drive benchmark directly.
Worked examples
- A file copy on a gigabit network. 2.5 GB copied in 30 seconds: 2,500 MB × 8 ÷ 30 = 666.7 Mbps, or 83.3 MB/s. On a 1 Gbps link that is 66.7% utilisation. Since wired gigabit typically peaks near 940 Mbps, the drives or the file protocol are probably holding the copy back.
- A download over Wi-Fi. 700 MB in 2 minutes is 700 × 8 ÷ 120 = 46.7 Mbps. On a 300 Mbps plan that is about 15.6% of the plan, so it is worth testing on a cable to see whether Wi-Fi or the server is the limit.
Throughput vs bandwidth vs speed tests
Bandwidth is the capacity of a link; throughput is what a particular transfer got out of it. Several things keep throughput below bandwidth: packet headers, Wi-Fi conditions, the speed of the far end, disk speed, and latency. On long-distance links a single TCP connection may not fill the pipe because it has to wait for acknowledgements; latency vs bandwidth covers why. Speed tests use several connections at once to measure capacity, which is why they often beat a single download. A low utilisation figure is therefore a prompt to look for the bottleneck, not proof that the link is faulty. If you want to judge a speed test against your plan instead, use the speed test checker.
Tips for accurate measurements
- Time only the transfer. Leave out connection setup and any unpacking at the end.
- Use a large single file. Many small files measure file-handling overhead as much as the network.
- Match units. If your operating system shows 2.5 GiB, that is about 2.68 GB; choose the binary unit so the result is not 7% low.
- Repeat. Run the transfer two or three times and use the typical result.
- Test wired first. Measuring over a cable removes Wi-Fi from the picture, so any remaining shortfall points to the far end, the disks or the protocol.
To predict how long a copy should take before you run it, use the file transfer time calculator; for server traffic over a month, the bandwidth calculator is the better fit.
Frequently asked questions
How do I calculate throughput from file size and time?
Convert the size to megabits (MB × 8) and divide by the seconds taken. For example, 2.5 GB in 30 seconds is 20,000 megabits ÷ 30 = 666.7 Mbps.
What is a good utilisation on a gigabit link?
For a single large transfer on wired gigabit, about 94% (around 940 Mbps) is the practical ceiling because of packet overhead. Results well below that usually point to disks, Wi-Fi, the far end or the protocol.
Why is my measured throughput lower than my speed test?
Speed tests use several parallel connections to nearby servers. A real transfer often uses one connection to a more distant or busier server, and may be limited by disk speed at either end.