GPS vs Car Speedometer Accuracy: Which One Is Closer to Real Speed?

Many drivers notice their vehicle speedometer and phone GPS speedometer show different values. In most cases, both are working as designed, but they use different measurement methods.

Why car dashboards often read higher

Most car speedometers are calibrated to avoid under-reporting speed.
Tire size, pressure, and wear can shift wheel-based speed readings.
Manufacturing tolerance may introduce small positive bias.

Why GPS speed can still vary

Poor satellite visibility in tunnels, dense cities, or heavy tree cover.
Device hardware quality and background power-saving limits.
Rapid acceleration where position updates lag by a short interval.

Practical recommendation

For day-to-day monitoring, use both readings as contextual guidance. For legal compliance, always follow the official instrument requirements in your region and prioritize safe driving practices.