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How Accurate Is Your Phone's GPS?

Under open sky, a phone's GPS position is typically within about 5 metres. Near tall buildings, under trees or indoors it can be tens of metres off. Speed is more accurate than position; altitude is less.

Updated 1 October 2026

The headline number

The US government's GPS site says GPS-enabled smartphones are "typically accurate to within a 4.9 m (16 ft.) radius under open sky", and that accuracy worsens near buildings, bridges and trees. That figure comes from a 2015 crowd test of more than a thousand phones, so it is an average from phones of that era, not a guarantee. Newer phones with dual-frequency receivers often do better in difficult places.

MeasurementTypical phone accuracy, open skyWhere it gets worse
Horizontal positionAbout 5 mCities, forests, indoors: often tens of metres
SpeedAbout 0.1 to 0.4 m/s (roughly 1 km/h)Hard acceleration, tight bends, reflections
GPS altitudeRoughly 1.5 times worse than horizontalAnywhere the sky is partly blocked

What the accuracy circle means

The blue circle around your dot, and the "±" figure apps show, is the device's own estimate of its error. In the web standard it is defined at 95% confidence: the true position should be inside the circle 19 times out of 20. iOS gives a similar per-fix estimate, horizontalAccuracy. A small circle means the receiver is confident, not that it is right. Reflected signals in a city can make it confidently wrong.

What makes GPS worse

Dual-frequency GPS: which iPhones have it

Older phones listen to one civil GPS frequency (L1). Dual-frequency phones also use L5 (and the matching Galileo E5a signal), which has more power and bandwidth. That helps reject reflected signals and correct the ionospheric delay. The first dual-frequency phone appeared in 2018. In Apple's specifications, "precision dual-frequency GPS" is listed for:

The standard iPhone 14, 15 and 16 (and their Plus models) and the iPhone 16e are single-frequency. Current iPhones listen to several satellite systems at once: GPS, GLONASS, Galileo, QZSS and BeiDou, plus India's NavIC on recent models. More satellites in view means more chances of good geometry when part of the sky is blocked.

Two things are often overstated: dual-frequency does not let GPS through walls or trees, and it does not make a phone accurate to a few centimetres. It makes the difficult cases better, and the easy cases a little better.

Altitude is the weak axis

All the satellites are above you, so the geometry that pins down height is worse than for position, and GPS height error is typically around one and a half times the horizontal error. GPS also measures height above a mathematical ellipsoid, not above sea level. Phones convert it with a geoid model. For smooth, precise height changes, the phone's barometer does much better. See barometric altimeter vs GPS altitude.

How to get the best fix

  1. Give the phone a clear view of the sky, top edge up if you can.
  2. Wait for the accuracy figure to settle before you mark a place. The first fix after a cold start is often the roughest.
  3. Move a few steps away from tall walls. Even a street's width can change the fix.
  4. Take the average of several fixes over a minute when marking something you need to find again.

Sources

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