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📡 Latency-to-Distance Calculator
Light in fiber travels at roughly 200,000 km/s — about 2/3 the vacuum speed of light. That bounds how fast a round-trip ping can possibly be. This calculator works both directions: enter a ping latency, see the max possible distance; or enter a distance, see the minimum theoretical ping. Use it to sanity-check CDN claims, or just to be amazed by how slow your home WiFi is compared to the speed of light.
Examples
NYC to LA (~4000 km)Min RTT 40 ms (real: 70-90 ms)Sydney to LA (~12,000 km)Min RTT 120 ms (real: 150-200 ms)50 kmMin RTT 0.5 ms (real: 5-10 ms with switching)Frequently asked questions
Why is my real ping much higher than the minimum?
Every hop adds switching/routing delay. WiFi adds 1-5 ms. ISP equipment, peering exchanges, and OS overhead each add more. Real-world ping is typically 2-3× theoretical for long distances.
Why is fiber slower than vacuum light?
Light slows in denser materials — refractive index of fiber is ~1.5, giving ~200,000 km/s vs ~300,000 km/s in vacuum. There is also some zigzag inside the fiber.
About this calculator
Latency-to-Distance Calculator runs entirely in your browser using standard formulas. No data is sent to any server. We don't share your inputs with lenders, brokers, or anyone else — there's no funnel and no follow-up email.
Related tools
- ⏱️ Bandwidth / Download Time Calculator — How long does an X GB file take at Y Mbps? Real-world download time.
- 📦 MTU / MSS Calculator — Compute MSS from MTU, account for IPsec/PPPoE/VLAN tunneling overhead.
Why this tool
vs typical free network-tools sites
| NetToolset | Typical free site | |
|---|---|---|
| Price | Free | Free |
| Signup required | No | Often (for advanced features) |
| Ads inside the tool | No | Yes (banner + interstitial) |
| Logs your IP / queries | No | Yes (often resold) |
| Data sent to a server | Math runs in browser; lookups hit Cloudflare DoH directly | Yes (all goes through their server) |
| Open source | Yes | No |
| Bookmarkable URL per tool | Yes | Mixed |
| Multilingual | EN / ES / PT / FR / DE | Usually EN only |
| Loads in under 1s | Yes (static) | Often slow (ad tracking) |