Written by Muneeb Rana · Last updated 26 October 2026
Quick answer: A speedometer for car use on your phone gives a second, GPS-based reading of your speed, plus trip distance, averages, a map and a HUD mirror for night driving. It is handy when a dashboard gauge is hard to read, broken, or reads high. Mount it, set it up before driving, and never handle it on the move.
TL;DR
- GPS speed as a cross-check.
- HUD mirror for night.
- Trip distance and averages.
- Mount securely; set up first.
- Dashboard is the legal reference.
Speedometer for car: setup
- Open Speedometer PRO before you move and allow precise location.
- Pick MPH or KM/H and the analog or digital meter.
- Tap Start on the Current Trip card if you want distance and averages.
- Mount the phone securely.
- Leave it alone until you stop.
Why drivers use one
- Compare with a dashboard that reads high (why)
- Large digital readout in older cars
- HUD mode at night
- Trip logs for expenses
- Rental cars with unfamiliar units
Mounting
See phone mount placement. Keep clear of airbags and the road view.
What it can't do
Speedometer PRO does not show speed limits, cameras or CarPlay. It relies on GPS, so tunnels interrupt it.
When the dashboard and app differ
It is normal for a car's speedometer to show a few mph more than GPS at steady speed, because regulations such as UN Regulation 39 forbid speedometers from showing less than true speed. A consistent small gap is expected; a large or changing gap may point to a tyre size change or a fault. Our speedometer error calculator shows the effect of tyre size.
Rental cars and abroad
Renting a car abroad often means unfamiliar units. Set the app to the local unit before you drive, so the readout matches road signs.
Using it as a temporary fix
If your car's speedometer fails, a phone app can show your speed until it is repaired, but in many places driving with a faulty speedometer is still an offence or an inspection failure. Get the car fixed promptly; the phone is a stopgap, not a replacement.
Legal
Many places ban holding a phone while driving; see phone use while driving laws.
Related: Speedometer use cases · GPS speedometer: live speed from your phone's satellites · Speedometer HUD mode for your windshield · GPS vs car speedometer: which one is right? · Phone mount placement: where to put your phone · Road trip tracker: log every leg
Get Speedometer PRO on Google Play · Download on the App Store · Set it up before you move; never handle your phone while driving.
Sources
- UN Regulation No. 39: speedometer and odometer (UNECE): unece.org (accessed 26 October 2026)
- Distracted Driving (NHTSA): nhtsa.gov (accessed 26 October 2026)
- GPS Accuracy (GPS.gov): gps.gov (accessed 26 October 2026)
- Head-up display (Wikipedia): en.wikipedia.org (accessed 26 October 2026)
- 49 CFR 571.101: controls and displays (eCFR): ecfr.gov (accessed 26 October 2026)
FAQ
Can I use my phone as a car speedometer?
Yes, as a secondary display. Your car's own speedometer remains the reference, especially in tunnels.
Is it legal to mount a phone on the windscreen?
It depends on where you live. Some places allow specific zones only.
Is the app more accurate than my car?
At steady speed in open sky it is often closer to true speed, because car speedometers read slightly high.
Does it work with CarPlay or Android Auto?
Not that we can confirm.
Will it drain my battery?
Charge the phone on longer drives; GPS and a bright screen use power.