0–60 timer: 0–60 mph and 0–100 km/h, timed by GPS.

The timer starts the moment your GPS speed leaves zero and stops the instant it crosses the target. Because phone GPS reports roughly once a second, the result is interpolated between the two fixes either side of the target speed — accurate to within about a tenth of a second in good conditions (see how accurate a GPS speed reading is), which is close enough to compare runs against each other.

Rarely, and that is normal. Published 0–60 times come from a prepared surface, a professional driver, a light fuel load and often a one-foot rollout allowance. A real car on a real road with passengers, a full tank and a cold gearbox will be slower. Use this to compare your own runs, not to argue with a brochure.

Wait until the accuracy reading settles under ±10 m, come to a complete stop, then accelerate in one continuous pull. Any coasting mid-run inflates the time. Mount the phone where it has a clear view of the sky — a windscreen mount beats a cup holder.

Acceleration testing belongs on a closed course or a private track, not a public road. Set the target and mount your phone before you move, and have a passenger operate it if you need to touch the screen at all.