Fiber Optic Latency Calculator
Estimate the one-way propagation delay of a fiber optic link from its distance.
Inputs
Saved Scenarios
— select 2+ to compare| Metric | |
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One-Way Delay (ms)
5.000
Round-Trip Delay (ms)
10.000
Spark says
How it's calculated
Formula
- 200{,}000
- — Approximate speed of light in fiber, in km/s (about 2/3 of light speed in vacuum)
What is the Fiber Optic Latency Calculator?
Light travels slower through fiber optic glass than through a vacuum — about 200,000 km/s due to the fiber's refractive index — setting a hard physical floor on latency that no amount of bandwidth or hardware can beat.
How to use it
- 1 Enter the physical distance the fiber link covers.
Worked examples
Limitations
- •This is propagation delay only — real-world latency also includes switching/routing delay at each hop, which typically adds more than the fiber itself over long-haul routes with many hops.
Frequently asked questions
Why is latency to a distant server always at least this much?
This is the physical speed-of-light floor for that distance — no network optimization can go faster, only closer to this theoretical minimum by adding fewer hops and more direct routes.