Why is my compass wrong in the car?

Metal, speakers and magnetic mounts disturb the magnetometer.

How do I calibrate it?

Move the phone in a figure-eight away from metal.

Speedometer With Compass: Heading on the Go

Written by Muneeb Rana · Last updated 26 October 2026

Quick answer: Speedometer PRO is a speedometer with compass built in. Besides the Speed and Map tabs, a Compass tab shows which way you are facing. Phone compasses use a magnetometer, which can be thrown off by metal and magnets in a car, so a quick figure-eight calibration and a mount away from speakers help keep the heading honest.

TL;DR

Compass is its own tab.
Uses the phone's magnetometer.
Car metal and magnetic mounts can skew it.
Magnetic north differs from true north.
Moving GPS course is a separate signal.

How a phone compass works

Phones contain a tiny magnetometer that senses Earth's magnetic field, combined with accelerometer and gyroscope data to work out which way the phone points. That gives a magnetic heading. Many apps convert it to true north using your location and the local magnetic declination, which NOAA publishes models for.

Calibrating

If the needle seems wrong, move the phone in a slow figure-eight a few times away from metal. Remove magnetic phone mounts or cases nearby; magnets right next to the sensor can push the heading off by many degrees. Inside a car, steel bodywork and speakers can also distort it.

Compass vs GPS course

When you are moving, GPS can also report your direction of travel, called course. That works even if the phone is mounted sideways, but it is meaningless when you stand still. The compass works stationary. Knowing the difference helps when they disagree.

Speedometer with compass: uses

Hiking and finding trailheads, orienting a map, sailing and paddling, or simply knowing which way a road heads in an unfamiliar city. Our compass directions explained guide covers the 16 compass points and degrees, and the online compass works in a browser.

Calibration

Phone compasses use a magnetometer, which can be thrown off by magnets in mounts, cases or nearby metal. If heading looks wrong, move the phone in a figure-of-eight to recalibrate, away from metal and magnets.

Compass vs course

While stationary, a compass shows which way the phone faces. While moving, GPS can give your course over ground, which may differ if the phone isn't aligned with the direction of travel.

Compass vs GPS heading

When you're moving, the app can take heading from GPS: the direction between successive fixes, which is accurate at speed and unaffected by magnets. When you're standing still, GPS heading is meaningless, so phones use the magnetometer instead. That sensor is easily disturbed by car speakers, metal mounts and magnetic cases, which is why a compass can read oddly inside a vehicle. If the direction looks wrong when stationary, move away from metal and follow your phone's calibration prompt.

Limits

The compass tab is for orientation, not navigation in hazardous terrain. Carry a proper compass and map for serious hiking or boating.

Get Speedometer PRO on Google Play · Download on the App Store · Set it up before you move; never handle your phone while driving.

Sources

Speedometer PRO・MPH Tracker (Google Play listing): play.google.com (accessed 26 October 2026)
Speedometer PRO・MPH Tracker (App Store listing): apps.apple.com (accessed 26 October 2026)
Compass (Wikipedia): en.wikipedia.org (accessed 26 October 2026)
Magnetic declination (NOAA NCEI): ncei.noaa.gov (accessed 26 October 2026)
Magnetic declination (Wikipedia): en.wikipedia.org (accessed 26 October 2026)