Why is the speed on Google Maps different from my car's speedometer and which is the real one?

Can you rely on the speed that Google Maps or another online speedometer shows you? Here we will clarify doubts about the speed shown by mobile apps.

Today we can measure the speed at which we are driving using mobile apps. In addition to Google Maps, which is included in the Android application package, there are also various third-party applications with a speedometer function, for example, the free iOS application Speedometer - How Fast Am I?, or the Android app GPS Speedometer and Odometer. If you use Google Maps or another navigation application on your car trips, then you probably noticed that the speed it shows is different from the speed on your speedometer. Why is this happening?

How does a car's speedometer work?

The classic car speedometer measures the rotation of the car's wheels and converts it into speed. Inside the speedometer is a mechanism that is connected to the driveshaft or transmission of the car. As the vehicle moves, the driveshaft or transmission rotates and turns the speedometer cable, which in turn sends these readings to your speedometer display. In modern cars, the speedometer is part of a whole combination of more complex instruments that includes other gauges such as the tachometer, fuel gauge and temperature gauge.

Most cars' speedometers slightly overestimate your speed. This is probably because their manufacturers want to avoid under-speeding, which would be much more dangerous for drivers.

Can you trust Google Maps speedometer? How accurate are the speed readings?

Google Maps is a handy tool for plotting the best routes, and also shows speed limit indicators and speed camera warnings based on user-reported information (however, speed radar warnings are not allowed in all countries). Recently, this application has also received a speedometer function, which is usually activated by default. Google Maps and other similar location-based apps work using GPS, which tracks your actual location over time, so their speed readings should, in principle, be more accurate. However, in practice, these applications are quite slow to respond to changes and may have errors. Therefore, if you want to always be on the safe side and avoid speeding tickets, it is still better to use your car's speedometer as a guide. You may drive a little slower, but it will be safer.