GPS speedometer in your browser
Tap “Start speedometer” and allow location access – your speed appears in large digits, with maximum, average, distance and time below. For cycling, hiking, trains or as a passenger.
How it is calculated
How to use the GPS speedometer
- Tap “Start speedometer” and allow location access.
- Wait a few seconds until the GPS signal is accurate enough. The speed appears large at the top.
- Choose a unit: km/h, mph, knots or m/s. Distance is shown in km, miles or nautical miles to match.
- “Stop” pauses, “Reset” clears top speed, distance and time.
How it measures
If the device provides a speed (W3C Geolocation API, “speed” in m/s), it is shown directly. Otherwise the tool calculates it from the distance and time between two positions. Distance is the great-circle distance (haversine formula after Snyder, USGS Professional Paper 1395) using the mean Earth radius of WGS 84. Conversions: 1 km/h = 1/3.6 m/s, 1 mph = 0.44704 m/s, 1 knot = 1852 m per hour (NIST).
To avoid “creeping” while standing still, movement only counts once it is larger than the inaccuracy of both positions. Points with more than 50 m inaccuracy and implausible jumps above 100 m/s are discarded.
Limits
- GPS needs a clear view of the sky; in tunnels, buildings and between tall buildings it drops out or becomes inaccurate.
- The browser must stay open with the screen on – many phones pause location in the background.
- Not a substitute for a vehicle speedometer and not a device for proving speed.
Frequently asked questions
How accurate is a GPS speedometer on a phone?
With good reception and steady movement it is usually quite usable. With weak signal, in curves or when accelerating, the value deviates more.
Can I use the GPS speedometer in a car?
Only as a passenger or mounted, without operating it while driving. The vehicle’s own speedometer always applies.
Why does it show a speed while I stand still?
The GPS position jitters slightly. The tool filters small jumps; with poor reception a value can still appear briefly.
Does it work in the background?
Usually not: many phones pause location when the browser is in the background or the screen turns off.
Is my route stored?
No. Positions are processed only in your browser and are neither stored nor sent.
Sources and legal basis
- W3C – Geolocation API
- MDN Web Docs – GeolocationCoordinates.speed
- Snyder, J. P.: Map Projections – A Working Manual, USGS Professional Paper 1395 (1987)
- NIST Special Publication 811 – Guide for the Use of the SI (conversion factors)
As of:
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