Network Latency Estimator
A network latency estimator calculates the minimum round-trip time physics allows between two points, then adds realistic overhead for cable routing and router hops. It explains why a request to a server 5,000 km away cannot complete in under 50 milliseconds no matter how fast the server is.
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Where the numbers come from
Light travels about 300,000 km per second in vacuum and about 200,000 km per second in optical fibre, because glass has a refractive index near 1.47. So each 1,000 km of fibre costs 5 ms one way and 10 ms round trip, before anything else happens. The estimator multiplies the straight-line distance by 1.25 because submarine cables and terrestrial routes follow coastlines and peering points rather than great circles, then adds roughly 0.25 ms per router in each direction for queuing and forwarding.
| Route | Distance | Physics minimum RTT | Typical measured RTT |
|---|---|---|---|
| New York to London | 5,570 km | 56 ms | 70 to 80 ms |
| London to Singapore | 10,850 km | 109 ms | 160 to 180 ms |
| San Francisco to Sydney | 11,950 km | 120 ms | 140 to 160 ms |
| Mumbai to Frankfurt | 6,570 km | 66 ms | 110 to 130 ms |
Why RTT matters more than bandwidth for small requests
Opening a TCP connection costs one round trip before any data flows. A TLS 1.3 handshake adds one more; TLS 1.2 adds two. So the first byte of an HTTPS response from a server 80 ms away arrives no sooner than 160 ms after the click on TLS 1.3, and 240 ms on TLS 1.2, regardless of connection speed. This is why CDNs place edge nodes near users and why HTTP/2 and HTTP/3 reuse connections aggressively.
What is left out
- Queuing delay under load, which is what makes ping times jitter.
- Wi-Fi retransmissions and mobile radio scheduling, which add 10 to 50 ms on the last hop.
- Geostationary satellite links, where the 35,786 km altitude alone forces around 500 ms RTT; low-earth-orbit constellations bring that to 25 to 60 ms.
Use the estimate to decide where to host relative to users, and to sanity-check a measured ping: if you are seeing 300 ms across a 2,000 km path, the problem is congestion or a bad route, not distance.
Related tools
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- Bandwidth Calculator — Calculate download times and bandwidth requirements. Convert between Mbps, MBps, and estimate transfer times for files.
- Download Speed Estimator — Estimate how long a download takes at a given connection speed, allowing for real-world overhead.
- API Latency Simulator — Simulate API response delays for testing application behavior under latency.
Frequently Asked Questions
Why is fibre slower than radio in the medium list?
Light slows down in glass. Fibre carries signals at roughly two-thirds of the vacuum speed of light, while microwave and free-space links run at nearly full speed. That is why some high-frequency trading routes use microwave towers instead of fibre.
How many hops should I enter?
Run a traceroute to the destination and count the lines. Cross-continent paths usually show 12 to 20 hops; within a metro area, 5 to 8.
Why is my measured ping higher than the estimate?
The most common reasons are a route that detours through a distant exchange point, congestion at a hop, or a wireless last mile. Compare with the physics minimum: if you are within about 1.5 times of it, the path is healthy.
Does bandwidth affect latency?
Not for a single small request. A 10 Gbps link and a 10 Mbps link deliver the first byte at the same time over the same distance. Bandwidth matters once the response is large enough that serialisation time dominates.
What RTT do TLS handshakes cost?
TLS 1.3 needs one round trip after the TCP handshake, so two in total before application data. TLS 1.2 needs two, three in total. Session resumption and HTTP/3 over QUIC reduce these on repeat connections.
Privacy & Security
Estimates calculated locally.
About This Tool
This tool runs entirely in your browser. No data is sent to any server, ensuring complete privacy. Simply use the interface above to get started — no registration or login required.
Disclaimer: This tool is provided "as is" without warranty of any kind. Results are for educational and utility purposes.
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