1 8 Mile Drag Racing Calculator

1/8 Mile Drag Racing Calculator

Estimate ET and Trap Speed based on Horsepower and Weight

Include driver and fuel weight.

Estimate power at the wheels.

Estimated Track Results

1/8 Mile ET

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Seconds

1/8 Mile Speed

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MPH

1/4 Mile ET (Est.)

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Seconds

1/4 Mile Speed (Est.)

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MPH

*Estimates assume ideal traction and weather conditions.

Understanding 1/8 Mile Performance

The 1/8 mile drag racing format is incredibly popular in regional circuits and small-town tracks. Because the distance is shorter (660 feet) than a traditional 1/4 mile, it focuses heavily on the "launch" and early acceleration of the vehicle. This calculator uses physics-based formulas to determine how much time (ET) and speed your car should achieve based on its weight and horsepower.

The Math Behind the Run

Drag racing performance is largely a function of the power-to-weight ratio. The formulas used in this tool are derived from the standard drag racing benchmarks:

• Elapsed Time (ET): Calculated using the formula 5.825 × ∛(Weight / HP).
• Trap Speed: Calculated using the formula 164 × ∛(HP / Weight).
• Conversion: To find the 1/4 mile equivalent, we apply a factor of 1.57 for time, though this varies based on gearing and aerodynamics.

Real-World Examples

Vehicle Setup	Weight	HP	Est. 1/8 Mile ET
Street Sedan	3,500 lbs	300 whp	8.84s
Muscle Car	3,800 lbs	650 whp	7.32s
Dragster	2,200 lbs	1,200 whp	5.42s

Variables That Affect Your Time

While horsepower and weight are the primary factors, several "hidden" variables will influence your real-world timeslip:

1. 60-Foot Time: The first 60 feet determine the whole run. Poor traction or a slow reaction can add significant time to your ET.
2. Density Altitude (DA): High humidity, high temperature, or high elevation thin the air, reducing your engine's power output.
3. Gearing: If your transmission gear ratios aren't optimized for 660 feet, you might be shifting at an awkward time, hurting your speed.
4. Suspension Setup: How the car transfers weight to the rear tires during the launch is critical for "hooking" rather than spinning.

function calculateDragStats() { var weight = parseFloat(document.getElementById("vehicleWeight").value); var hp = parseFloat(document.getElementById("wheelHP").value); if (isNaN(weight) || weight <= 0 || isNaN(hp) || hp <= 0) { alert("Please enter valid positive numbers for both weight and horsepower."); return; } // 1/8 Mile Formula for ET: ET = 5.825 * (Weight / HP)^(1/3) var et18 = 5.825 * Math.pow((weight / hp), 1/3); // 1/8 Mile Formula for Speed: Speed = 164 * (HP / Weight)^(1/3) var speed18 = 164 * Math.pow((hp / weight), 1/3); // 1/4 Mile Estimates (Common conversion factors) var et14 = et18 * 1.57; var speed14 = speed18 * 1.26; // Display Results document.getElementById("et18").innerText = et18.toFixed(3); document.getElementById("speed18").innerText = speed18.toFixed(2); document.getElementById("et14").innerText = et14.toFixed(3); document.getElementById("speed14").innerText = speed14.toFixed(2); document.getElementById("dragResults").style.display = "block"; } function resetDragStats() { document.getElementById("vehicleWeight").value = ""; document.getElementById("wheelHP").value = ""; document.getElementById("dragResults").style.display = "none"; }