Your phone already has everything a speedometer needs. This GPS speedometer reads your speed from satellite signals, so it does not care about wheel size, tyre wear or the vehicle you are in.
Tap Start GPS and allow location access
A normal speedometer counts how fast the wheels turn. A GPS speedometer has no connection to the wheels. Your phone receives signals from several satellites, and as you move, the frequency of each signal shifts very slightly, the Doppler effect. The GPS chip turns those shifts into a speed, about once a second. That is why GPS speed is smooth and accurate even though a single GPS position can be off by several metres.
| GPS speedometer | Wheel speedometer | |
|---|---|---|
| Measures | Movement over the ground | Wheel rotations |
| Affected by tyre wear | No | Yes |
| Set to read high | No | Yes, by design |
| Works in tunnels | No | Yes |
| Works on a train, plane or boat | Yes | No |
At a steady speed under open sky, a phone GPS speedometer is usually within 1 to 2 km/h of the true speed. During hard acceleration or braking it lags by a second or so. In cities with tall buildings, signals bounce, and readings get less reliable.
More detail in how GPS calculates speed and how Zpeedometer works.
Tap Start GPS above and allow location access. The speedometer uses your phone's GPS receiver to show live speed in km/h, mph, m/s or knots. Your location stays on your device.
Give the phone a view of the sky. In a car, the dashboard or a windscreen mount works better than a pocket or the footwell. Wait for the accuracy figure on the gauge to settle before you trust the speed, which takes a few seconds after you start. Turn off battery saver modes, as some reduce GPS updates.
Anywhere there is no speedometer: a train, bus, ferry, plane seat by the window, a bicycle, or on foot. It also gives a neutral reference for checking a car or motorcycle speedometer, because it is not affected by the vehicle at all.
It uses the Doppler shift in satellite signals, along with changes in position, to work out how fast you are moving over the ground, about once a second.
Yes. At a steady speed with a clear view of the sky it is usually within 1 to 2 km/h, which is often closer than a car speedometer.
Only to load this page. GPS signals come from satellites, so the speed keeps working without mobile data.
Satellite signals are weak and are blocked by roofs and walls. Move near a window or outside.
Often, yes, from a window seat, if your airline allows GPS in flight mode. Expect speeds of 800 to 900 km/h at cruise.