# Tokyo, Japan → London, UK RTT

🇯🇵 **Tokyo, Japan (TYO)** → 🇬🇧 **London, UK (LON)**

Measurement round: `2026-08-16T04:07:28Z`.

In the 2026-08-16T04:07:28Z round, ICMP echo probes from Tokyo to London returned an average round-trip time of 202.7 ms across 50 samples, with a minimum of 196.6 ms and a maximum of 224.34 ms. No packets were lost, and jitter was 4.9 ms.

The great-circle distance between Tokyo and London is about 9,582 km. If light could travel that distance in a vacuum, the floor would be 63.93 ms; a direct fiber path would be roughly 93.84 ms. The observed average is 2.16 times that fiber floor, so this route is operating at about 46.3% of the direct-fiber ideal.

This path ranked 15th among the 19 outbound routes from its starting point, placing it in the slower half of that set. Its own variation-to-average ratio was about 2.8%, below the 3.28% midpoint across the set, and the standard deviation of 5.6 ms shows stable round-trip times despite the Fair latency tier.

## Latency Summary

| Metric               | Value                                                      |
| -------------------- | ---------------------------------------------------------- |
| RTT                  | **202.7 ms**                                               |
| Jitter               | **4.9 ms**                                                 |
| Packet Loss          | **0%**                                                     |
| Standard Fiber Floor | **93.84 ms**                                               |
| Fiber Efficiency     | **46.3%**                                                  |
| Latency Tier         | Fair                                                       |
| Source Region        | [Asia Pacific](/docs/network/latency/regions/asia-pacific) |
| Destination Region   | [Europe](/docs/network/latency/regions/europe)             |

## Ping Measurement Series

The chart below renders the 50-sample ICMP echo measurement round for this route; an accessible table of every sample is included with the chart.

## Download This Route's Data

This route's measurement round is published as open data (CC BY 4.0) in CSV, JSON, and YAML. See [About This Measurement](#about-this-measurement) for citation guidance.

## Theoretical Fiber Latency

The public physical reference uses the GeoNames city centres for [Tokyo](https://www.geonames.org/1850147) (35.68950, 139.69171) and [London](https://www.geonames.org/2643743) (51.50853, -0.12574). It does not disclose either facility address.

| Physical Reference                            | Value          |
| --------------------------------------------- | -------------- |
| WGS-84 geodesic distance                      | **9,582.1 km** |
| Vacuum RTT floor                              | **63.93 ms**   |
| Standard fiber RTT floor ($n_g=1.4679$)       | **93.84 ms**   |
| Low-latency fiber material floor              | **93.46 ms**   |
| Engineering floor (5% path allowance)         | **98.54 ms**   |
| Research 1.33× mapped-fiber reference         | **124.8 ms**   |
| Estimated unamplified path loss               | **2012.2 dB**  |
| Transparent optical spans / inline amplifiers | **126 / 125**  |
| Published RTT inflation over fiber floor      | **2.16×**      |

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](/docs/network/latency/theoretical-fiber-latency).

## Stability & Trend

The current measurement round (2026-08-16T04:07:28Z) collected 50 ICMP echo samples on this route. Distribution statistics from that round:

| Round Statistic    | Value         |
| ------------------ | ------------- |
| Minimum RTT        | **196.6 ms**  |
| Average RTT        | **202.7 ms**  |
| Maximum RTT        | **224.34 ms** |
| Standard deviation | **5.6 ms**    |
| Stdev / average    | **2.8%**      |

## Route Context

* Departure PoP: [Tokyo (TYO)](/docs/network/latency/tyo-tokyo)
* Destination PoP: [London (LON)](/docs/network/latency/lon-london)
* Region overview: [Asia Pacific](/docs/network/latency/regions/asia-pacific) → [Europe](/docs/network/latency/regions/europe)
* Full global matrix: [Backbone Latency Matrix](/docs/network/latency)
* Physical methodology: [Theoretical Fiber Latency](/docs/network/latency/theoretical-fiber-latency)

## Related City-Pair Routes

**Reverse direction**

* [London to Tokyo latency and RTT](/docs/network/latency/pairs/lon-tyo-rtt) — 202.9 ms

**Fastest routes departing Tokyo (TYO)**

* [Tokyo to Taipei latency and RTT](/docs/network/latency/pairs/tyo-tpe-rtt) — 32.3 ms
* [Tokyo to Hong Kong latency and RTT](/docs/network/latency/pairs/tyo-hkg-rtt) — 44.8 ms
* [Tokyo to Singapore latency and RTT](/docs/network/latency/pairs/tyo-sin-rtt) — 69.4 ms
* [Tokyo to Seattle latency and RTT](/docs/network/latency/pairs/tyo-sea-rtt) — 84.8 ms
* [Tokyo to Los Angeles latency and RTT](/docs/network/latency/pairs/tyo-lax-rtt) — 101.2 ms

**Fastest routes arriving at London (LON)**

* [Amsterdam to London latency and RTT](/docs/network/latency/pairs/ams-lon-rtt) — 5.2 ms
* [Paris to London latency and RTT](/docs/network/latency/pairs/par-lon-rtt) — 6.4 ms
* [Frankfurt to London latency and RTT](/docs/network/latency/pairs/fra-lon-rtt) — 12.9 ms
* [Berlin to London latency and RTT](/docs/network/latency/pairs/ber-lon-rtt) — 15.2 ms
* [Marseille to London latency and RTT](/docs/network/latency/pairs/mrs-lon-rtt) — 18.9 ms

**Same corridor (Asia Pacific → Europe)**

* [Hong Kong to Moscow latency and RTT](/docs/network/latency/pairs/hkg-mow-rtt) — 118.2 ms
* [Taipei to Moscow latency and RTT](/docs/network/latency/pairs/tpe-mow-rtt) — 132.7 ms
* [Singapore to Marseille latency and RTT](/docs/network/latency/pairs/sin-mrs-rtt) — 140.6 ms

## About This Measurement

Published RTT reflects best-case backbone path behavior measured with ICMP echo probes between PoPs. End-user latency also depends on local access networks, congestion, routing policy, and traffic engineering. None of these values is an SLA.

The measurement round behind this page is published as open data under **CC BY 4.0** in the [Hats Network latency dataset](/opendata/latency/). Per-pair files are available at `/opendata/latency/latest/pairs/tyo-lon.pings.{csv,json,yaml}`. When citing, include the route, the measurement round timestamp, and the dataset version — for example: "Hats Network latency dataset, Tokyo → London round 2026-08-16T04:07:28Z, CC BY 4.0".

***

*Data auto-generated on August 16, 2026. Explore the [full interactive latency matrix](/docs/network/latency) or browse more [city-pair routes](/docs/network/latency/pairs).*

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## License and attribution

- **Canonical source:** [View the human-readable HTML page](https://hatsnet.io/docs/network/latency/pairs/tyo-lon-rtt).
- **Original documentation:** © Hats Network Inc., licensed under [CC BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0/).
- **Public latency data:** © Hats Network Inc., licensed under [CC BY 4.0](https://creativecommons.org/licenses/by/4.0/).
- **Full terms:** [Content and Data License](https://hatsnet.io/docs/legal/content-and-data-license) — includes attribution requirements, third-party material, trademarks, source code and other exclusions.