How this calculator works
A transfer moves bytes over a link that carries bits. Convert the data size to bits by multiplying by eight, then divide by the link throughput in bits per second. The result assumes the link is dedicated and error free. Real bulk copies are slower because the storage at each end, the protocol and the distance all add overhead, and many small files transfer far more slowly than one large file of the same total size.
Formula
transfer time (s) = data size (bytes) x 8 / throughput (bits per second). data size (bytes) = throughput x transfer window / 8. throughput (bits per second) = data size x 8 / transfer window.
Worked example
Moving 4 GB over a 50 Mbit/s link: 4,000,000,000 bytes x 8 = 32,000,000,000 bits. Dividing by 50,000,000 bits per second gives 640 seconds, which is 10 minutes 40 seconds. On a 1 Gbit/s link the same data takes 32 seconds in theory, but disk throughput and protocol overhead usually keep a real copy well above that.
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Frequently asked questions
Should I plan for the theoretical time?
No, treat it as a lower bound. Network overhead, encryption, disk speed and the number of files each add time. For planning, add 10 to 30 percent for a single large file over a good link, and much more for many small files or a long-distance link.
Does the data size change with the unit?
The number shown changes, the data does not. A 4 GB file is 3.73 GiB. This page converts both to bytes before dividing, so choosing MB, MiB or GB gives the same transfer time.
Why does a backup with many small files take so long?
Each file costs a round trip of its own, so a folder of a million tiny files is limited by latency rather than bandwidth. Putting the files in an archive first, or using a tool that batches requests, often cuts the time dramatically.
Can I use this for cloud egress planning?
Yes for the time estimate. Remember that cloud providers price egress by volume and may throttle sustained transfers outside a service tier, so the effective throughput can drop after a short burst.