pjhtech Tools
Link & transport

Bandwidth-Delay Product Calculator

Estimate bytes in flight from bottleneck bandwidth and round-trip delay.

Input

Time to the other endpoint and back, not one-way latency.

Reset restores the example inputs.

Local calculation · inputs are not sent to a server.

Result

Calculating the example…

Enter the path’s bottleneck bandwidth in Mbps and its end-to-end round-trip time in milliseconds. The result is the approximate amount of unacknowledged data needed to fill that path; compare it with the connection’s available TCP window.

Example: 1 Gbps with a 20 ms round trip gives 2,500,000 bytes, approximately 2441.41 KiB. A 64 KiB window alone would not fill this idealized path.

Use RTT, not one-way delay. A window below this estimate can limit throughput, but the result is not a socket-buffer setting: TCP window scaling, autotuning and congestion control also affect the connection. A zero RTT gives a mathematical zero, not a useful sizing estimate.

References