Quarter Mile Calculator: Estimate Your ET & Trap Speed
Free quarter mile calculator using proven formulas. Estimate your 1/4 mile ET and trap speed from horsepower and weight. Then verify with real GPS timing.
How to Use the Calculator
- Enter your vehicle's weight in pounds (include fuel, driver, and modifications)
- Enter your vehicle's horsepower (SAE, wheel HP, or estimated dyno HP)
- The calculator instantly shows your estimated quarter mile ET and trap speed
- Your result falls into a performance bracket (sub-10s, 10-11s, 11-12s, etc.)
The Formula: Brock Yates / Roger Huntington
This calculator uses the industry-standard Brock Yates quarter mile prediction formula, used by performance engineers and drag racers for decades. The formulas are:
- ET = 5.825 × (Weight ÷ HP)^(1/3) — Estimates quarter mile elapsed time
- Trap Speed = 234.24 × (HP ÷ Weight)^(1/3) — Estimates terminal velocity at the finish line
These formulas were developed by analyzing thousands of drag racing results and remain surprisingly accurate for initial estimates.
Accuracy and Limitations
The Brock Yates formula typically estimates within ±0.3 to ±0.5 seconds for street cars with good traction. However, real-world results depend heavily on factors the calculator cannot measure:
- Traction and grip — A car with poor traction will be much slower than the formula predicts
- Launch technique — Bad launches cost 0.3–0.5 seconds. The formula assumes perfect execution
- Weather — Hot days and high altitude can add 0.3–0.7 seconds versus optimal conditions
- Gearing — Poorly matched gears lose power off-the-line or waste potential top-end speed
- Transmission efficiency — Slipping automatics vs. well-shifted manuals, CVTs, and dual-clutch boxes perform differently
- Road surface — A grippy drag strip surface vs. asphalt vs. concrete makes a huge difference
Performance Brackets: What is a Good Quarter Mile Time?
| Bracket | Range | Typical Examples |
|---|---|---|
| Sub 10s | Under 10.0 seconds | Twin-turbo, supercharger, high-boost, 400+ hp |
| 10–11s | 10.0–10.99 seconds | Turbo 4-cyl, naturally-aspirated V8, 300+ hp |
| 11–12s | 11.0–11.99 seconds | Turbo 4-cyl, V6, light modifications, 250+ hp |
| 12–13s | 12.0–12.99 seconds | Stock 300+ hp cars, tuned 4-cyl, 200+ hp |
| 13–14s | 13.0–13.99 seconds | Stock sport cars, 250–300 hp |
| 14s+ | 14.0 seconds and above | Stock standard sedan, economy cars |
Why GPS Timing Beats Any Calculator
A calculator gives you a starting point, but real GPS timing shows you actual results. FastTrack uses GPS Doppler-derived speed combined with 100Hz accelerometer launch detection to measure 0-60 and quarter mile times with accuracy within ±0.02 seconds.
When you use the calculator and then verify with real GPS data, you learn exactly how your car performs in your conditions. You can then use mod-aware leaderboards to see which upgrades actually produce the fastest times for your platform.
Download FastTrack Free on the App Store
Timing feature page | View all guides | FastTrack vs Dragy
Frequently Asked Questions
How accurate is the quarter mile calculator formula?
The Brock Yates formula is accurate within ±0.3 seconds for typical street cars. It works well for estimating performance but does not account for traction, launch technique, weather, or altitude. Real-world results vary significantly. GPS timing provides much more accurate data for your specific vehicle and conditions.
What factors affect quarter mile time besides horsepower?
Major factors include: traction and grip (tire quality, surface, launch technique), weight distribution, gearing, transmission efficiency, weather (temperature, humidity, barometric pressure), altitude, suspension setup, and driver skill. A car with more weight can sometimes outrun one with less if it has better traction or gearing.
Is a phone GPS accurate enough for quarter mile timing?
Yes. FastTrack produces quarter-mile ETs within ±0.04 seconds and trap speed within ±0.3 mph. It fuses GPS Doppler velocity with a 100Hz accelerometer using the same class of sensor-fusion math used on Apollo 11 and in modern self-driving cars. That lands inside the accuracy range of a standard Dragy — and costs nothing.
What is a good quarter mile time for a street car?
Average street cars (200–300 hp, 3,000–3,500 lbs) run 14–16 second quarter miles. Sporty cars run 12–14 seconds. Performance cars run 10–12 seconds. Truly fast cars (400+ hp, tuned) run under 10 seconds. The formula helps you estimate where your car should fall in this range.
How do I improve my quarter mile time?
Improve ET by: (1) increasing horsepower (turbo, supercharger, tune), (2) reducing weight, (3) improving traction (better tires, suspension, launch technique), (4) optimizing gearing for your powerband, (5) reducing rolling resistance, (6) improving launch control. Each change shifts your ET estimate. GPS timing lets you verify improvements and compare setup changes.