About this tool
Transfer time depends on file size, link speed and the percentage of line rate that the application can actually use. A nominal 1 Gbps path does not mean a large file will move at exactly 1 Gbps end to end.
This calculator applies an efficiency factor so planning estimates can reflect protocol overhead and real-world limitations. It is useful for backups, image transfers, replication and maintenance planning.
How to use it
- Enter the file size and unit.
- Enter the link speed in Mbps.
- Enter an efficiency estimate, then calculate the expected transfer duration.
Example: 25 GB over 1 Gbps at 90% efficiency
The effective rate is 900 Mbps. A 25 GB decimal file contains about 200 gigabits, so the transfer takes roughly 222 seconds, or a little under four minutes.
Engineering notes
- Long-distance TCP transfers may need window tuning to fill a high-bandwidth path when latency is significant.
- If the path contains a slower segment, shape/police rate or application cap, use the real bottleneck rather than the fastest interface speed.
Frequently asked questions
What efficiency percentage should I use?
For rough planning, 90–95% is often reasonable on a healthy path, but real applications can be much lower. Use measured data when available.
Does latency matter?
Yes, especially for TCP. High latency can limit throughput when the receive window or congestion-control behavior cannot keep enough data in flight.
Does this account for compression?
No. Enter the amount of data that actually needs to cross the network or adjust the estimate separately.