Propagation Delay Calculator

What Is Signal Propagation Delay?

Propagation delay is how long an electrical or optical signal takes to travel from sender to receiver. In networks, PCB traces, and RF links, delay depends on path length and how fast the medium carries the wave — slower than light in vacuum when signals travel through cable dielectric.

Propagation Delay Formula

$$\text{delay} = \frac{d}{c \times VF}$$

$d$ is distance, $c$ is the speed of light ($2.998 \times 10^8$ m/s), and $VF$ is the velocity factor (0 to 1). A 3 m polyethylene Ethernet cable with $VF = 0.65$ has delay $\approx 15.4$ ns.

Velocity Factor by Medium

Air and vacuum use $VF = 1$. Typical Cat 5/6 polyethylene cable uses about 0.65. PTFE and foam dielectrics are faster; PVC is slower. High-frequency PCB design and network timing analysis both rely on this value.

Frequently Asked Questions

What is velocity factor?

Velocity factor is the fraction of the speed of light at which a signal propagates in a cable or medium. It depends on the dielectric material.

Why is delay important in networking?

Propagation delay sets a floor on round-trip time. It matters for latency-sensitive trading, gaming, and distributed systems even when bandwidth is high.

Is propagation delay the same as latency?

Latency includes propagation delay plus processing, queuing, and serialization time. Propagation delay is only the travel time along the path.

What velocity factor should I use for Ethernet?

Polyethylene (PE) Cat 5/6 cable is commonly 0.65. Use 1.0 for wireless or satellite paths through air.

How do I convert delay to nanoseconds?

Divide distance by propagation speed in m/s, then multiply by $10^9$. This calculator displays ns, µs, ms, or seconds automatically.

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What Is Signal Propagation Delay?

Propagation Delay Formula

Velocity Factor by Medium

Frequently Asked Questions

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