Propagation Delay Calculator

How to Use Propagation Delay Calculator

• Enter the physical path distance, not the data size. Use m, km, mile, or ft as appropriate.
• Select a medium preset: air, optical fiber, copper cable, or custom velocity factor.
• Use custom factor when you know a cable dielectric velocity factor from a data sheet.
• Read one-way delay for a single trip and round-trip delay for request/response timing.

Formula & Theory - Propagation Delay Calculator

v = c × velocity_factor
one_way_delay = distance / v
RTT ≈ 2 × one_way_delay
c = 299,792,458 m/s

Propagation delay is the time a signal spends traveling through the medium. It is separate from serialization delay, queueing delay, routing delay, and software processing time.

The velocity factor expresses signal speed as a fraction of the speed of light. Fiber is often around 0.67 because light travels slower in glass than in vacuum.

Real network paths may be longer than map distance because cables follow routes, ducts, seabed paths, and patch panels. The distance input should represent actual path length when possible.

Use Cases for Propagation Delay Calculator

• Estimating latency floor between cities or data centers.
• Checking fiber or copper cable delay in timing-sensitive systems.
• Explaining why long-distance links cannot beat the speed-of-light limit.
• Separating propagation delay from bandwidth or packet-processing effects.