1/8 Mile to 1/4 Mile ET Calculator
Predict your full quarter-mile performance based on your eighth-mile timing slips.
Estimated 1/4 Mile Statistics
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— mph
*Estimates are based on standard industry multipliers (1.57x ET and 1.25x Speed). Actual results may vary based on vehicle aerodynamics and top-end gearing.
Understanding the 1/8 to 1/4 Mile Conversion
For many drag racers, 1/8 mile tracks are more accessible or common than full 1/4 mile strips. However, the 1/4 mile (1320 feet) remains the gold standard for performance benchmarking. This calculator uses mathematical constants derived from thousands of drag racing passes to project what your vehicle would likely run if the track kept going for another 660 feet.
The Math Behind the Prediction
The most widely accepted "rule of thumb" in the drag racing community is the 1.57 multiplier. While every car is different, most door-slammers and street-legal cars follow a predictable acceleration curve once they have cleared the initial 660 feet.
- Predicted 1/4 Mile ET: 1/8 Mile ET × 1.57
- Predicted 1/4 Mile Trap Speed: 1/8 Mile MPH × 1.25
Common Conversion Benchmarks
If you are looking for quick reference points, here are some common 1/8 mile times and their 1/4 mile equivalents:
| 1/8 Mile ET (sec) | 1/4 Mile ET Prediction | Category |
|---|---|---|
| 4.50 | 7.06 | Pro Mod / Outlaw |
| 5.70 | 8.95 | Super Comp / Fast Bracket |
| 6.40 | 10.05 | Street/Strip Muscle |
| 7.65 | 12.01 | Modern Performance |
| 9.55 | 15.00 | Stock Daily Driver |
Factors That Influence Your "Back Half"
It is important to remember that a calculator provides a theoretical estimate. Real-world performance can vary based on several factors:
- Aerodynamics: High-horsepower cars with poor aerodynamics (like bricks) will slow down more in the second half of the track compared to streamlined dragsters.
- Gearing: If your car reaches its maximum RPM or runs out of gears shortly after the 1/8 mile mark, your 1/4 mile time will be significantly slower than predicted.
- Power Adder Type: Nitrous cars often have a massive hit in the 1/8 mile but may "taper off" depending on the tune, whereas large turbochargers often "pull" harder in the back half (the 1/4 mile).
- Weight: Heavier cars require more energy to maintain acceleration at high speeds, often leading to a slightly higher multiplier than 1.57.
Why do we use the 1.57 Multiplier?
The 1.57 constant is used because it accounts for the fact that the car is already moving at a high rate of speed when it crosses the 1/8 mile mark. Unlike the first 660 feet, which includes the "dead stop" and the launch (the most time-consuming part), the second 660 feet is covered while the vehicle is at full throttle and peak velocity.