Speedometer Test — Check Your True Speed Online

How to run a speedometer test

1. Tap START above and allow location access.
2. Drive (or ride) at a steady speed — for example hold your dashboard needle exactly at 60 km/h or 40 mph.
3. Compare the GPS reading on this page with your dashboard. The GPS figure is your true ground speed.
4. Repeat at 2–3 different speeds (city, highway) for a complete speedometer accuracy test.

What is a speedometer test?

A speedometer test compares the speed shown on your vehicle's dashboard against your real, GPS-measured ground speed. Because regulations require vehicle speedometers to never read low, manufacturers calibrate them 3–10% high — so at an indicated 100 km/h your true speed is often only 92–97 km/h. This free online speed test reveals the exact difference for your vehicle, with no app or OBD device needed.

Reading your test result

• GPS reads 3–8% lower than the dashboard — normal factory calibration; your speedometer is healthy.
• GPS reads higher than the dashboard — your speedometer under-reports; you may be speeding without knowing. Common after fitting larger tires. Get it checked.
• Difference over ~10% — possible fault, wrong tire size, or worn tires; worth a mechanic visit.

Why speedometers become inaccurate

Vehicle speedometers measure wheel rotation, so anything that changes wheel circumference changes the reading: new tire sizes, tire wear, low pressure, or lift kits. GPS is unaffected by all of these — it measures how your position actually changes per second, which is why it's the standard reference for a speed test.

Speedometer test for any vehicle

This test works for cars, motorcycles, buses, trucks, trains and bicycles. For boats, switch the unit to knots. All you need is a phone with GPS and a clear view of the sky.

Tips for an accurate test

1. Test on a straight, flat road — curves and slopes add small errors.
2. Hold the speed steady for at least 5–10 seconds before comparing.
3. Check the GPS Accuracy tile: under 10 m means the reading is highly reliable.
4. Do several runs at different speeds and average the difference.

How to enable website location on your phone?

First, go to your device settings and turn on Location, then follow these steps:

Step 1: Open SpeedometerOnline.com and tap the Lock icon at the top of your browser.

Step 2: Tap the Permissions option.

Step 3: Tap the switch to enable Location access.

Step 4: The switch should now look like this — turned on.

Step 5: Refresh the page — it will start showing your travelling speed.

More free tools on this site