# Sydney, Australia → London, UK RTT

🇦🇺 **Sydney, Australia (SYD)** → 🇬🇧 **London, UK (LON)**

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

The 2026-08-16T04:07:28Z round of 50 ICMP echo probes from Sydney to London produced an average round-trip time of 256.5 ms, a minimum of 243.5 ms, and a maximum of 279.39 ms. Packet loss was zero, while jitter reached 10.31 ms and standard deviation 9.98 ms.

With a great-circle distance of 16,988.9 km, the theoretical fiber-floor RTT is 166.37 ms. The observed average is about 1.54 times that floor, so the route operates at roughly 64.9% fiber efficiency, leaving about 90 ms of overhead beyond the ideal fiber path.

The route ranked 15th of 19 outbound paths from Sydney for this round, and its variability is around 3.9% of the average, slightly above the 3.28% median for the route set. Jitter being slightly larger than the standard deviation highlights that individual round trips varied more irregularly than the overall dispersion alone suggests; the zero-loss profile remains clean. As with any ICMP RTT view, these numbers describe network-layer round-trip delay rather than end-user application performance.

## Latency Summary

| Metric               | Value                                                      |
| -------------------- | ---------------------------------------------------------- |
| RTT                  | **256.5 ms**                                               |
| Jitter               | **10.31 ms**                                               |
| Packet Loss          | **0%**                                                     |
| Standard Fiber Floor | **166.37 ms**                                              |
| Fiber Efficiency     | **64.9%**                                                  |
| Latency Tier         | High                                                       |
| 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 [Sydney](https://www.geonames.org/2147714) (-33.86785, 151.20732) 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                      | **16,988.9 km** |
| Vacuum RTT floor                              | **113.34 ms**   |
| Standard fiber RTT floor ($n_g=1.4679$)       | **166.37 ms**   |
| Low-latency fiber material floor              | **165.7 ms**    |
| Engineering floor (5% path allowance)         | **174.71 ms**   |
| Research 1.33× mapped-fiber reference         | **221.27 ms**   |
| Estimated unamplified path loss               | **3567.7 dB**   |
| Transparent optical spans / inline amplifiers | **223 / 222**   |
| Published RTT inflation over fiber floor      | **1.54×**       |

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        | **243.5 ms**  |
| Average RTT        | **256.5 ms**  |
| Maximum RTT        | **279.39 ms** |
| Standard deviation | **9.98 ms**   |
| Stdev / average    | **3.9%**      |

## Route Context

* Departure PoP: [Sydney (SYD)](/docs/network/latency/syd-sydney)
* 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 Sydney latency and RTT](/docs/network/latency/pairs/lon-syd-rtt) — 258.1 ms

**Fastest routes departing Sydney (SYD)**

* [Sydney to Melbourne latency and RTT](/docs/network/latency/pairs/syd-mel-rtt) — 9.8 ms
* [Sydney to Singapore latency and RTT](/docs/network/latency/pairs/syd-sin-rtt) — 94.5 ms
* [Sydney to Tokyo latency and RTT](/docs/network/latency/pairs/syd-tyo-rtt) — 101.3 ms
* [Sydney to Taipei latency and RTT](/docs/network/latency/pairs/syd-tpe-rtt) — 131.7 ms
* [Sydney to Hong Kong latency and RTT](/docs/network/latency/pairs/syd-hkg-rtt) — 135.7 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/syd-lon.pings.{csv,json,yaml}`. When citing, include the route, the measurement round timestamp, and the dataset version — for example: "Hats Network latency dataset, Sydney → 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/syd-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.