WintelGuy.com
WAN Latency Estimator

Enter a number in either field, then click outside of the text box.

Distance in:
Distance between sites:
Fibre path adjustment:
   %
Metro fibre & local loop length:
Speed of light in fibre:
/ millisecond
Equipment latency:
     millisecond
Round-trip time (RTT):
millisecond

Notes:
The primary purpose of this tool is to estimate WAN latency based on the light signal propagation time over a fibre link. This tool does not take into account any additional delays that may be introduced by communication protocols, routing, encryptions, data transformation, etc.

See also:
Network throughput calculator...
How fast does light travel through a fibre optic cable?
What is Network Latency and Why Does It Matter? - by O3b Networks.