A GPS speedometer for trains, bikes, boats and walks
This GPS speedometer shows how fast you are moving right now, using the location sensor in your phone or laptop. It is handy as a train speed meter (how fast is this train really going?), on a bicycle or e-scooter, on a boat in knots, or just for curiosity on a walk. Alongside the live reading you get your top speed, your average speed while moving, your average including stops, the trip distance and the time moving.
Press Start tracking and allow location when your browser asks. The page never asks on its own, it keeps the numbers only in memory while it is open, and nothing is uploaded. If you switch to another tab, tracking stops by itself, so the page does not keep using your location in the background.
How to use the GPS Speedometer
- Press Start tracking and choose Allow when the browser asks for your location.
- Wait a few seconds for a GPS fix; near a window or outdoors works best, deep inside a carriage or building may not.
- Pick km/h, mph, knots or m/s from the unit list. The readings convert instantly.
- Read the speed, top speed, averages and distance; press Reset to start a new trip, and Stop when finished.
- Copy the summary if you want to note down the trip.
GPS Speedometer features
Four units
km/h, mph, knots and metres per second, with distance in km, miles, nautical miles or metres to match.
Top and average speed
Top speed, average while moving and average including stops, using only fixes with a good accuracy.
Accuracy shown
The browser’s accuracy radius appears with the speed; weak fixes are ignored rather than adding phantom distance.
Stops when hidden
Tracking ends when the tab is hidden, and your totals stay until you reset.
Private
Positions stay in memory and are never sent or saved.
How the speed is measured
Browsers expose the Geolocation API, which reports a position every second or so and, on devices with a GPS receiver, a speed in metres per second taken from the Doppler shift of the satellite signals. That is usually more accurate than working out speed from successive positions. If the device gives no speed, this page derives it from the distance between two good fixes divided by the time between them.
Distance is the sum of the straight-line steps between fixes whose accuracy is 50 m or better and that moved at least 2 m, so GPS jitter while you stand still does not build up as distance. Speeds are converted exactly: 1 m/s is 3.6 km/h, 2.237 mph or 1.944 knots. The average while moving counts only the seconds when your speed was at least 0.5 m/s (1.8 km/h).
| m/s | km/h | mph | knots |
|---|---|---|---|
| 5 | 18 | 11.2 | 9.7 |
| 10 | 36 | 22.4 | 19.4 |
| 27.8 | 100 | 62.1 | 54.0 |
| 55.6 | 200 | 124.3 | 108.0 |
Limits and safe use
Do not use it while driving. Looking at a screen takes your eyes off the road; give it to a passenger, or use it on a train, bus, boat or bike where it is safe to look. It is not a calibrated speedometer and must not be used to contest a speeding ticket or to enforce a limit.
GPS speed is smoothed and can lag by a second or two, so a sudden brake or acceleration appears late. Accuracy falls in tunnels, cuttings, between tall buildings, inside metal carriages and on cold-started phones, and some browsers give a coarse location when precise location is off. Speed is zero until the first fix. Check the accuracy figure under the speed: if it is worse than a few tens of metres, trust the number less. For converting between units, see the speed converter.
GPS Speedometer FAQ
Can I use it as a train speed meter?
Yes, as a passenger. Sit by a window for the best signal; the speed is the train’s GPS speed, not the timetable speed.
Does it work without internet?
The GPS works offline, but the page itself must be loaded first. Mobile data is not needed for the speed reading.
Why is the speed 0 or blank?
Either you have not pressed Start or allowed location, there is no fix yet, or you are standing still. Wait for an accuracy figure to appear.
How accurate is it?
Typically within about 1 km/h on open ground when the accuracy radius is small. It is worse in tunnels and cities. It is not certified for enforcement.
Does it use battery or data?
GPS tracking uses battery while the tab is open. It sends no data, and stops when you hide the tab.
Can I use it while driving?
No. Do not look at your phone while driving. Use it only as a passenger or on transport where you are not driving.