Note: Calculations are based on standard drag racing conversion factors (1.57x for ET, 1.25x for Speed). Results may vary based on gearing, aerodynamics, and traction.
function calculateQuarterMile() {
// Get input values
var etInput = document.getElementById('eighthEt').value;
var speedInput = document.getElementById('eighthSpeed').value;
// Parse floats
var eighthEt = parseFloat(etInput);
var eighthSpeed = parseFloat(speedInput);
// Conversion factors
// Standard industry average is often cited as 1.57
// High horsepower cars might be lower (1.55), slower cars higher (1.60)
var etFactor = 1.57;
var speedFactor = 1.25; // Roughly 1.24 to 1.27 depending on power band
var quarterEt = 0;
var quarterSpeed = 0;
var hasSpeed = false;
// Validation & Calculation
if (isNaN(eighthEt) || eighthEt 0) {
quarterSpeed = eighthSpeed * speedFactor;
hasSpeed = true;
}
// Display Logic
document.getElementById('resultsArea').style.display = "block";
document.getElementById('quarterEtResult').innerText = quarterEt.toFixed(3) + " sec";
if (hasSpeed) {
document.getElementById('quarterSpeedResult').innerText = quarterSpeed.toFixed(2) + " mph";
} else {
document.getElementById('quarterSpeedResult').innerText = "N/A";
}
}
How to Convert 1/8 Mile Times to 1/4 Mile Estimates
Drag racing enthusiasts often find themselves at tracks that only run the eighth-mile distance, usually due to space constraints or safety regulations for faster vehicle classes. However, the quarter-mile remains the "gold standard" benchmark for vehicle performance in the automotive world. This calculator allows racers and tuners to translate their 1/8 mile time slips into estimated 1/4 mile performance metrics.
The Conversion Math
While no formula can perfectly predict a car's performance due to variables like aerodynamics, gearing ratios, and traction at the top end of the track, statistical averages provide a highly accurate estimation for most street and strip vehicles.
The standard conversion factors used in this calculator are:
Elapsed Time (ET): 1/8 Mile ET × 1.57 = 1/4 Mile ET
The conversion factor of 1.57 is widely accepted as the average for most street cars. However, specific vehicle setups may vary:
High Horsepower / Forced Induction: Cars with massive top-end power (turbocharged) may have a lower conversion factor (e.g., 1.55) because they pull harder in the back half of the track.
Quick Launch / Low Power: Vehicles that launch hard but run out of steam (often naturally aspirated or geared very short) may see a higher factor (e.g., 1.59 or 1.60), as they don't accelerate as aggressively after the 1/8 mile mark.
Aerodynamics: Boxy vehicles (like trucks or Jeeps) encounter significant wind resistance at high speeds, often resulting in slower quarter-mile trap speeds than the 1.25x multiplier would suggest.
Common Time Benchmarks
Use this reference table to see where common performance benchmarks align:
1/8 Mile ET
Estimated 1/4 Mile ET
Performance Tier
6.37 sec
10.00 sec
Pro Street / Supercar
7.00 sec
10.99 sec
Highly Modified Street
7.64 sec
11.99 sec
Modern Muscle Car
8.28 sec
12.99 sec
Performance Sport Compact
8.92 sec
14.00 sec
Average Sports Sedan
Why Race 1/8 Mile?
Many racers prefer or are forced to race the 1/8 mile for several reasons. Firstly, many local tracks are limited in length. Secondly, 1/8 mile racing emphasizes the launch and the 60-foot time, which effectively tests suspension tuning and driver reaction without putting as much stress on the engine at sustained high RPMs. Finally, it is often considered safer for extremely fast cars, as trap speeds are significantly lower, providing more stopping distance.