Estimate round-trip latency from distance using the speed of light in fibre, plus per-hop and processing overhead.
Propagation is pure physics: light in glass covers about 200 km per millisecond, so a 8,000 km link costs roughly 80 ms of round trip before anything else, and a realistic cable route adds another 40%. Hop and processing overheads are added on top, and a cold request pays roughly three round trips for DNS, TCP and TLS before the first byte arrives. No amount of server tuning beats the speed of light, so once the propagation floor exceeds your latency target the only fix is moving the endpoint closer — which is precisely the argument for an edge deployment.
Global Latency
RTT = 2 × great-circle distance × route factor ÷ signal speed in fibre, plus 2 × hops × per-hop delay; roughly 1 ms per 100 km in each direction.
RTT = 2 × great-circle distance × route factor ÷ signal speed in fibre, plus 2 × hops × per-hop delay; roughly 1 ms per 100 km in each direction. Propagation is pure physics: light in glass covers about 200 km per millisecond, so a 8,000 km link costs roughly 80 ms of round trip before anything else, and a realistic cable route adds another 40%. Hop and processing overheads are added on top, and a cold request pays roughly three round trips for DNS, TCP and TLS before the first byte arrives.
No amount of server tuning beats the speed of light, so once the propagation floor exceeds your latency target the only fix is moving the endpoint closer — which is precisely the argument for an edge deployment.
This calculator takes 6 inputs: Great-circle distance, Fibre path vs straight line, Signal speed in fibre, Router hops on the path, Queueing and forwarding per hop, Server processing time. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.