GPS Speedometer — Car Speed Test

Modern phone GPS is very accurate for speed — typically within about 1 km/h when you have a clear view of the sky and are moving steadily. It reads speed directly from the GPS signal (the same Doppler method sat-nav uses), not just distance over time. Accuracy drops in tunnels, dense cities and under heavy tree cover, where the signal is weaker.

Yes. GPS itself doesn't need the internet — it uses satellites. Once the page is open, speed is measured from GPS on your device, so it keeps working offline. A connection only helps the first fix lock on a little faster.

It shows 0 when you're not moving, or before GPS has locked on. If it stays at 0 while you're moving, you're likely indoors or somewhere with a weak signal — move to an open area, and make sure location access is allowed and GPS is switched on.

Kilometres per hour (km/h), miles per hour (mph) and knots. Tap the unit at the top to switch — max speed, average and distance all update to match.

Yes, it's completely free with no sign-up, no app to install and no watermark. Everything runs right in your browser.

Keeping GPS and the screen on does use battery, like any navigation or map app. To save power, lower your screen brightness and tap Stop when you're not measuring. Charging while you use it in a car is a good idea on long trips.

When you tap Start, your browser asks for location — tap Allow. If you blocked it earlier, open the site permissions (the padlock icon in the address bar, or your phone's app settings) and set Location to Allow, then tap Start again. Also make sure your phone's GPS/Location toggle is on.

Yes. It works for any moving activity — cycling, running, driving, boating (use knots) or other sports. It measures your speed over the ground regardless of the vehicle.

HUD (head-up display) mode mirrors the numbers left-to-right and enlarges them. Place your phone flat on the dashboard and the display reflects the right way round in your windshield, so you can read your speed without looking down.

Often, yes. Car speedometers are legally allowed to read a little high (they must never read low), so they usually show a few km/h more than your true speed. GPS measures your actual speed over the ground, which is why it can read slightly lower than the dashboard.