VaneHow to Time 0 to 60 mph With Your Phone's GPS
A phone can time your car or bike from 0 to 60 mph using nothing but its GPS. Done right it is good to a few tenths of a second, and it will usually read slower than the published figure, for a reason that has nothing to do with the phone.
Updated 26 October 2026
Only on a closed road or a track. Never time acceleration on a public road. Everything below assumes a place where it is legal and safe to do it.
How a GPS timer works
A phone does not get its speed by dividing distance by time. Its satellite receiver measures speed directly from the Doppler shift of the signals, which is why a phone's speed is good to a few tenths of a metre per second even when its position wanders by several metres. Our explainer on how GPS measures speed has the detail.
The catch is timing. A phone reports a new speed about once a second. In a quick car, 60 mph arrives between two of those readings, and the timer has to work out when. How well it does that decides the result:
- The start. The car begins to move somewhere inside the first second; a good timer works it out from the readings that follow rather than waiting for the next one.
- The finish. The moment the speed crosses 60 mph lies between a reading below it and one above it.
- Gear changes. A shift inside that second bends the speed curve, so a run with a change near the finish is less certain than a clean pull.
Put together, a phone can time a typical 0 to 60 mph run to within about two or three tenths of a second. Dedicated GPS timing boxes that report ten times a second do better, which is why serious testers use them; a phone is a fair everyday tool, not a lab.
Why your time is slower than the brochure
Most US magazines, and many manufacturers' figures, use a one-foot rollout: the clock starts only after the car has already moved about 30 cm, the way a drag strip's timing beam works. By then the car is doing a few miles an hour, and roughly 0.3 seconds has gone. A phone starts the clock when the car starts to move, so your honest time is the published one plus that rollout. Some testers publish both numbers for this reason.
| Published (with rollout) | From standstill, roughly |
|---|---|
| 3.0 s | 3.3 s |
| 6.0 s | 6.3 s |
| 9.0 s | 9.3 s |
Load, temperature, altitude (thinner air costs a non-turbo engine power), tyre wear and the surface all move the number too.
0 to 60 mph or 0 to 100 km/h?
100 km/h is 62.1 mph, so the metric run is a little longer: typically a few tenths of a second for the same car. For towing or overtaking, a rolling test such as 50 to 70 mph or 80 to 120 km/h says more about how a car feels on the road than a standing start does.
How to get a clean run
- Mount the phone where it will not slide, with a view of the sky through the windscreen. Not in a pocket or the footwell.
- Wait for a good fix. Give the phone a minute in the open before the first run. Trees, buildings and bridges overhead weaken the signal.
- Choose a level stretch. A 1% slope is worth about 0.01 g, enough to move a slow car's time noticeably.
- Run both ways and average to cancel out slope and wind.
- Repeat. Three runs that agree tell you more than one quick one.
Sources
- Wikipedia, Rollout (drag racing): the one-foot rollout and its effect on 0–60 times.
- Li et al., smartphone Doppler velocity, ISPRS Archives XLVI-3/W1 (2022): 0.1 to 0.4 m/s on the move.
- Supej & Čuk (2014), comparison of GNSS devices for measuring speed: the lag of receivers that report once a second.
- Apple, CLLocation.speedAccuracy.
Common questions
Can an iPhone measure 0 to 60 accurately?
To a few tenths of a second, on a clear road with a good satellite fix. GPS measures speed well, but a phone reports it about once a second, so the exact moment you pass 60 mph has to be estimated between two readings.
Why is my 0-60 time slower than the manufacturer's?
US magazines and many manufacturers start the clock only after the car has rolled the first foot, which takes about 0.3 seconds off. A phone times from the moment the car starts moving. Load, temperature, tyres and the road surface matter too.
Is 0-100 km/h the same as 0-60 mph?
Almost. 100 km/h is 62.1 mph, so a 0 to 100 km/h time is a little longer than a 0 to 60 mph time for the same car, typically by a few tenths of a second.