TCP throughput calculator
The real speed a TCP connection reaches for a given link, delay, window size and packet loss.
From ping between the two sites.
Window:
Runs in your browser. Nothing you type is sent to the server.
About this tool
One TCP connection cannot send faster than its window divided by the round-trip time, and packet loss lowers the ceiling further. That is why a 1 Gbps link between distant sites can still copy slowly. Enter the link speed, the round-trip time from ping and the window size; the result is the speed one connection can reach, what limits it, and how many parallel streams you would need to fill the link. The loss figure uses the Mathis estimate for standard TCP with a 1460 byte segment, so treat it as a guide, not a measurement.