Network Latency Calculator (Fibre Distance)
How much latency does distance add to a network path?
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Network Latency Calculator (Fibre Distance) by TheCalcTools
How the Network Latency Calculator (Fibre Distance) works
Enter the straight-line distance, a route stretch factor and any fixed equipment delay.
Light in fibre travels at about 200,000 km/s, roughly two thirds of the speed in a vacuum, so each 1,000 km adds about 5 ms.
Round trip is twice the one-way delay plus equipment delay.
The formula
Worked example
Using the default values shown in the calculator:
| One-way distance (km) | 1000 |
|---|---|
| Route stretch factor | 1.4 |
| Equipment and processing delay (ms, round trip) | 2 |
- Route length = 1,000 × 1.4 = 1,400 km.
- One-way propagation = 1,400 ÷ 200 = 7.00 ms.
- Round trip = 14.00 ms + 2 ms equipment = 16.00 ms.
Result:
| One-way propagation (ms) | 7.00 |
|---|---|
| Round-trip propagation (ms) | 14.00 |
| Estimated round-trip time (ms) | 16.00 |
| Route length (km) | 1,400 |
Frequently asked questions
Why is latency not lower with a faster link?
Bandwidth does not change the speed of light in fibre. Distance sets a hard minimum on latency.
What speed does light travel in fibre?
About 200,000 km/s, because the refractive index of glass is around 1.47.
Sources and further reading
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