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# Propagation Delay

JustinLiller.Propagation Delay

The **Propagation Delay** calculator compute the propagation delay based on the positions of two routers and the propagation speed.

**INSTRUCTIONS:** Choose units and enter the following:

- (
**A**) This is the position of router A on the network - (
**B**) This is the position of router B on the network - (
**S**) This is the propagation speed

**Propagation Delay (PD):** The calculator returns the delay in milliseconds (ms). However this can be automatically converted to compatible units via the pull-down menu.

#### Related Calculators

- Simplified Propagation Delay
- Propagation Delay
- Nodal Delay
- End to End Delay
- RF Velocity of Propagation
- Cable dB Loss Budget
- Transmission Delay

#### The Math / Science

The formula for propagation delay is:

PD = ( A - B) / S

where:

- PD is the propagation delay
- A is the position of router A
- B is the position of router B
- S is the propagation speed

Once a bit is pushed into the link, it needs to propagate to router B. The time required to propagate from the beginning of the link to router B is the propagation delay. The bit propagates at the propagation speed of the link. The propagation speed depends on the physical medium of the link (that is, fiber optics, twisted-pair copper wire, and so on) and is in the range of `2*10^8 "meters/sec" to 3* 10^8 "meters/sec"` which is equal to, or a little less than, the speed of light. The propagation delay is the distance between two routers divided by the propagation speed.