London to Seattle Latency, Ping & RTT | AS203314
London to Seattle ping and RTT: 125.2 ms, 1.41 ms jitter, 75.63 ms fiber floor, and 60.4% efficiency across AS203314. Updated 2026-07-19.
🇬🇧 This page compares the published ping and round-trip time (RTT) from London (LON) to 🇺🇸 Seattle (SEA) with vacuum and optical-fiber physical limits.
Latency Summary
| Metric | Value |
|---|---|
| RTT | 125.2 ms |
| Jitter | 1.41 ms |
| Packet Loss | 0% |
| Standard Fiber Floor | 75.63 ms |
| Fiber Efficiency | 60.4% |
| Latency Tier | Good |
| Source Region | Europe |
| Destination Region | North America |
Theoretical Fiber Latency
The public physical reference uses the GeoNames city centres for London (51.50853, -0.12574) and Seattle (47.60621, -122.33207). It does not disclose either facility address.
| Physical Reference | Value |
|---|---|
| WGS-84 geodesic distance | 7,722.7 km |
| Vacuum RTT floor | 51.52 ms |
| Standard fiber RTT floor () | 75.63 ms |
| Low-latency fiber material floor | 75.32 ms |
| Engineering floor (5% path allowance) | 79.42 ms |
| Research 1.33× mapped-fiber reference | 100.58 ms |
| Estimated unamplified path loss | 1621.8 dB |
| Transparent optical spans / inline amplifiers | 102 / 101 |
| Published RTT inflation over fiber floor | 1.66× |
Attenuation is used to estimate the number of 80 km optical spans; it does not directly slow light. See the full theoretical fiber latency, GeoNames, attenuation, and amplifier methodology.
Stability & Trend
The following estimated indicators summarize route stability for the current publication period and are intended for comparative planning rather than SLA evaluation.
| Stability Indicator | Value |
|---|---|
| Minimum RTT | 123.6 ms |
| Median RTT (p50) | 124.9 ms |
| 95th percentile RTT (p95) | 127.3 ms |
| Maximum RTT | 127.9 ms |
| Jitter | 1.41 ms |
| Packet loss | 0% |
RTT trend
Estimated route stability across the selected time window.
- Average
- 125.2 ms
- Minimum
- 124.0 ms
- Maximum
- 126.4 ms
- Average loss
- 0.02%
Route Context
- Departure PoP: London (LON)
- Destination PoP: Seattle (SEA)
- Region overview: Europe → North America
- Full global matrix: Backbone Latency Matrix
- Physical methodology: Theoretical Fiber Latency
Related City-Pair Routes
- Reverse direction: Seattle to London latency and RTT — 124.3 ms
- London to Amsterdam latency and RTT — 5.1 ms
- London to Paris latency and RTT — 6.3 ms
- London to Frankfurt latency and RTT — 12.4 ms
- London to Berlin latency and RTT — 16 ms
- London to Marseille latency and RTT — 17.3 ms
About This Measurement
Published RTT reflects best-case backbone path behavior. End-user latency also depends on local access networks, congestion, routing policy, and traffic engineering. Stability indicators are comparative estimates, and none of these values is an SLA.
Data auto-generated on July 19, 2026. Explore the full interactive latency matrix or browse more city-pair routes.