Support
ZeroTo times your car's acceleration with nothing but your iPhone: 0–60 mph, 0–100 km/h, the eighth and quarter mile, gear shifts and the slope of the road. If something doesn't work, or you have a question, write to us.
Email shchukavlad4@gmail.com. We usually reply within two business days. For a question about a specific run, open it and use Export → Export raw sensor log, then attach the file.
How does a phone measure acceleration?
GPS reports your speed about once a second. That's too slow to catch the moment you launch, so ZeroTo also reads the motion sensors 100 times a second. They pick up the moment the car starts to roll and fill the gaps between GPS readings. GPS, in turn, keeps the speed from drifting. The result is worked out right after the run.
How accurate is it?
A phone can't fully match a dedicated 10–25 Hz GPS box, but using both sensors gets closer than GPS alone, especially at the start of the run. Accuracy is best with the phone firmly mounted, on a flat road with open sky. Each run gets a quality grade and a road slope, so you can see when a time shouldn't be compared. Under Results you can also open "Compare with GPS alone" to see what a GPS-only timer would have shown.
Getting a good run
- Use a phone mount. A phone lying loose on a seat or in a cup holder moves around and spoils the result.
- Find an open, flat, closed road or a track. Tall buildings and trees weaken GPS.
- Stop fully, tap Start recording and wait for "Ready". Then launch. The timer starts by itself.
- Lift off when you're done. Recording stops on its own when the car slows down.
- Compare runs in both directions of the same road to cancel out slope and wind.
Why does ZeroTo need Location and Motion & Fitness?
Precise Location gives speed and distance. Motion & Fitness lets the app read the barometer, which measures the slope of the road. Without either one the times would be wrong or unverifiable, so the app asks for both before the first run. Both stay on your phone. If you turned one off, go to iPhone Settings → ZeroTo.
It never says "Ready"
"Ready" needs a GPS fix (give it up to half a minute outdoors the first time) and a phone that isn't moving. Make sure the car is stopped and the phone is firmly in its mount.
What do the gear shift numbers mean?
When the gearbox changes gear, the push you feel drops for a moment. ZeroTo times that drop for every shift, shows how deep it was and how much time it cost. Shorter and shallower is quicker, so it's a good way to compare drive modes or a gearbox tune.
ZeroTo Pro
Every run is measured with the same accuracy for everyone. Pro is a one-time purchase that adds more intervals (60–130 mph, 100–200 km/h, 0–200 km/h, 60 ft, 1/2 mile, rollout), every gear shift in detail, a garage with any number of cars, unlimited history, CSV export and share cards without the ZeroTo mark. To restore Pro on a new device, open Settings → Restore Purchases.
Please drive safely
Use ZeroTo only on closed roads or tracks where it's legal, and keep your eyes on the road. You never need to touch the phone during a run.