Home · Calculators
Drag Racing Calculators
Every calculator free, every formula shown. They pre-fill from your saved combo, so you type your car's numbers once — not once per tool.
ET & Horsepower
Horsepower from ET
Estimate horsepower from weight and elapsed time
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Horsepower from MPH
Estimate horsepower from weight and trap speed
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ET Predictor
Predict elapsed time from weight and horsepower
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MPH Predictor
Predict trap speed from weight and horsepower
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1/8 ↔ 1/4 Mile Converter
Convert eighth-mile times to quarter-mile estimates
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Weather-Corrected ET
Correct your ET to standard sea-level air
Open calculator →Weather, Air & Fuel
Density Altitude
Calculate density altitude from your local weather conditions
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Jetting Change
Size a jet change for changing air density
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E85 Mix
Blend gasoline and E85 to a target ethanol content
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Injector Sizing
Size fuel injectors for horsepower, fuel and duty cycle
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Fuel Pump Sizing
Size fuel pump flow for your horsepower goal
Open calculator →Engine Math
Compression Ratio
Calculate static compression ratio from engine volumes
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Dynamic Compression
Calculate dynamic compression with your cam timing
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Cranking Pressure
Estimate cranking compression pressure from dynamic ratio
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Displacement
Calculate engine displacement from bore and stroke
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Head Flow & Power
Estimate horsepower potential from cylinder head airflow
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Port Velocity
Calculate intake port velocity from flow and area
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Carburetor CFM
Size a carburetor for displacement and maximum RPM
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Piston Speed
Calculate mean and maximum piston speed from stroke
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Boost Horsepower
Estimate horsepower gain from boost pressure
Open calculator →Gears, Tires & Converter
Gear Ratio / RPM / MPH
Calculate gear ratio from ring and pinion teeth
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Tire Diameter & Rollout
Calculate overall tire diameter from the sidewall size
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Gear & Speed Table
See speed in every gear across your RPM range
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Tire Size Change
Compare old and new tires for effective gearing change
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Converter Slip
Calculate torque converter slip at the finish line
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Shift Point / RPM Drop
Calculate RPM drop between gears at the shift
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Speedometer Correction
Find speedometer error after gear or tire changes
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Rollout
Calculate tire rollout and revolutions per mile
Open calculator →Off-road? The Garage math family includes RegearReady's regear calculators.
Calculators give you numbers. The Tuning System gives you memory. The $39 Tuning System adds the run logbook, DA/jetting tracker and change planner that turn one-off answers into a season of data.