1/8 Mile Calculator
Convert 1/4 mile times to 1/8 mile performance estimates
How to Use
- Enter your 1/4 mile elapsed time (ET) in seconds
- Enter your 1/4 mile trap speed
- Select your speed unit (MPH or KPH)
- Click calculate to see your estimated 1/8 mile performance
- Review your eighth-mile ET, trap speed, and 60-foot time
What is 1/8 Mile Drag Racing?
1/8 mile drag racing is a shortened version of traditional 1/4 mile drag racing, covering 660 feet (201 meters) instead of 1,320 feet. It's popular at smaller tracks, for street cars, and in regions where space or safety concerns make quarter-mile racing impractical.
Eighth-mile racing emphasizes launch technique and early-stage acceleration more than top-end speed. Many street car enthusiasts prefer 1/8 mile because it's less stressful on vehicles and requires less space while still providing exciting competition.
Understanding Conversion Ratios
Converting between 1/8 mile and 1/4 mile times uses industry-standard ratios that have been validated through extensive testing:
- ET Conversion: 1/8 mile ET ≈ 64% of 1/4 mile ET (multiply by 0.64)
- Speed Conversion: 1/8 mile trap speed ≈ 76% of 1/4 mile trap speed (multiply by 0.76)
- 60-Foot Time: Approximately 10-11% of 1/4 mile ET
- These ratios are most accurate for typical street and bracket racing cars
- Pro Stock and extremely fast cars may show different ratios due to power curves
For example, a car running 12.00 seconds at 115 MPH in the 1/4 mile would typically run approximately 7.68 seconds at 87.4 MPH in the 1/8 mile.
Benefits of 1/8 Mile Racing
Many racers choose eighth-mile racing for several practical reasons:
- Requires less space - ideal for smaller tracks or street-legal events
- Reduced stress on vehicles - less time at high speed means less wear and tear
- Lower speeds at finish line - safer for inexperienced drivers
- Emphasizes driver skill in launch and early acceleration
- More passes per event - quicker turnaround times
- Lower chance of catastrophic failure at extreme speeds
- Better for testing combinations without full commitment to quarter-mile speeds
The Importance of 60-Foot Times
The 60-foot time measures how long it takes to travel the first 60 feet from the starting line. This is one of the most critical numbers in drag racing, especially for 1/8 mile racing:
| ET Range (1/4 Mile) | Target 60-Foot Time | Performance Level |
|---|---|---|
| 7-9 seconds | 1.00-1.20 seconds | Pro level |
| 10-11 seconds | 1.30-1.50 seconds | Very fast street/bracket |
| 12-13 seconds | 1.60-1.90 seconds | Fast street |
| 14-15 seconds | 2.00-2.30 seconds | Moderate street |
| 16+ seconds | 2.30+ seconds | Stock/street |
Improving your 60-foot time through better launch technique, tire pressure, and suspension setup can dramatically improve overall ET, especially in 1/8 mile racing where the launch represents a larger percentage of the total run.
Factors Affecting Conversion Accuracy
While conversion ratios are generally accurate, several factors can cause actual results to vary:
- Power delivery characteristics - turbo lag, nitrous activation points, or supercharger boost curves
- Gear ratios - cars that shift at the 1/8 mile mark may see different ratios
- Aerodynamics - high-speed drag becomes more significant in the second half of the quarter mile
- Weight distribution - affects how the vehicle accelerates throughout the run
- Track conditions - temperature, humidity, and track prep affect different parts of the run differently
- Traction issues - spinning tires early affects the ratio significantly
Frequently Asked Questions
- How accurate is the 1/8 mile to 1/4 mile conversion?
- The standard conversion ratios (64% for ET, 76% for speed) are generally accurate within 2-5% for most street and bracket racing cars. However, factors like power delivery, gearing, and aerodynamics can affect accuracy. Use these estimates as guidelines rather than exact predictions.
- Why is 1/8 mile racing becoming more popular?
- Eighth-mile racing requires less space, is safer at the finish line with lower speeds, puts less stress on vehicles, and emphasizes driver skill in launch and early acceleration. Many street car enthusiasts and smaller tracks prefer it over quarter-mile racing.
- Can I convert 1/8 mile times to 1/4 mile times?
- Yes, but with less accuracy. Divide your 1/8 mile ET by 0.64 to estimate 1/4 mile ET, and divide your 1/8 mile trap speed by 0.76 to estimate quarter-mile speed. However, this reverse conversion is less reliable because it's harder to predict how a car will accelerate in the second half of the quarter mile.
- What's a good 60-foot time for my car?
- A good 60-foot time depends on your vehicle's power and setup. Generally, aim for approximately 10-11% of your quarter-mile ET. For example, a 12-second car should target around 1.6-1.8 seconds. Improving your 60-foot time through better launch technique can significantly improve your overall ET.