How Accurate Is a Qibla Direction?
The geographic bearing can be calculated very precisely from two coordinate pairs. Real-world accuracy also depends on the starting location, sensor quality and how the direction is transferred into the room.
Calculation accuracy
QiblaPoint calculates the initial great-circle bearing from your coordinates to the Kaaba. More precise starting coordinates produce a more location-specific answer.
Device accuracy
GPS accuracy and compass accuracy are separate. A phone may know where it is while its magnetic heading is disturbed. Sensor cases, magnets, nearby metal and an uncalibrated compass are common causes.
A practical accuracy check
Use the exact bearing, inspect the map and transfer the line to a distant visible feature. If the phone compass disagrees sharply with that map reference, recalibrate it and move away from interference.
Use the live Qibla finder for your exact position, or choose a published bearing from the city directory.