FREE RACE TOOLS / STAGED LAB

NUMBERS DON’T LIE.

Free drag racing calculators for gearing, tire size, trap RPM, and approximate performance planning.

TRAP RPMTIRE SIZEGEARINGET ESTIMATES

TRACKSIDE MATH

RUN THE NUMBERS.

01 / DRIVETRAIN

Trap RPM

Estimate engine RPM at a given speed. Transmission ratio and converter slip are adjustable.

Trap speed (MPH)

Rear gear ratio

Tire diameter (in)

Transmission ratio

Converter slip (%)

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Uses RPM ≈ MPH × axle ratio × transmission ratio × 336 ÷ tire diameter, adjusted for estimated converter slip. Actual results vary with tire growth, loaded radius, and drivetrain conditions.

02 / TIRES

Tire Diameter

Convert a metric street tire size into approximate overall diameter.

Section width (mm)

Aspect ratio (%)

Wheel diameter (in)

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Nominal diameter = wheel diameter + 2 × (section width × aspect ratio ÷ 100) ÷ 25.4. Actual tire dimensions vary by manufacturer and rim width.

03 / DRIVETRAIN

Speed at RPM

Estimate theoretical speed from RPM, gearing, and tire height.

Engine RPM

Rear gear ratio

Tire diameter (in)

Transmission ratio

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Assumes zero converter slip and no tire growth. Not a prediction of actual track performance.

04 / PERFORMANCE

Estimated HP from ET

Very rough quarter-mile horsepower estimate based on race weight and elapsed time.

Race weight with driver (lb)

Quarter-mile ET (sec)

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Uses the common ET approximation HP ≈ weight ÷ (ET ÷ 5.825)³. This is a rough empirical estimate, not a dyno measurement; do not use 1/8-mile ET in this formula.

Important: These are planning estimates, not a substitute for measured track data, professional tuning, or safety inspections.