HowFast – Drag Race Predictor

DtimesTwo Technologies

Contains adsIn-app purchases

About this app

Know your number before you stage.
HowFast predicts your elapsed time using your vehicle's real specs — engine, drivetrain, tires, and the air conditions at your track. Whether you're dialing in for bracket racing or just curious how quick your car really is, HowFast gives you a data-driven starting point that gets smarter every time you run.
Predict with confidence HowFast builds your ET prediction from the ground up — horsepower, drivetrain loss, tire grip, shift times, and real-time density altitude correction. The more you run, the more accurate it gets. HowFast learns from your actual timeslips and adjusts future predictions automatically.
Built for the track, not the spec sheet No expensive GPS hardware required. Use your iPhone's built-in GPS for run detection and timing, or connect a RaceBox or Qstarz external GPS for precision timing at up to 25Hz. HowFast automatically detects your run and starts logging — no tapping required.
Your logbook, always with you Every run is saved with your predicted ET, actual ET, speed, and conditions. Review your history, spot trends, and see how your tune is progressing over the season.
Upgrade to Pro — one time, yours forever Unlock the full HowFast experience with a single one-time purchase:
* OBD-II gear detection — see what gear you're in, in real time
* Multi-run comparison — overlay runs to find where you're gaining or losing
* Unlimited vehicles in your garage
* CSV export — take your data anywhere
HowFast Pro is a one-time purchase. No subscription, no recurring charges.
Whether you're a seasoned bracket racer chasing a perfect dial or a weekend warrior seeing what your car can do, HowFast is the smartest co-driver you've never had.

What’s new

Track name now displays in run detail logs. Bug fixes on telemetry graphing.