Automotive Calculators
Built for the Shop

Compare two tire sizes side by side — diameter, circumference, sidewall height, revolutions per mile, and speedometer error.

Calculate fuel economy in MPG, L/100km, and cost per mile from distance traveled and fuel used. Compare trips and track fuel spending.

Convert between horsepower and torque at a given RPM. Also calculate HP from trap speed or ET and vehicle weight.

Calculate vehicle speed from RPM, gear ratio, final drive, and tire size — or find RPM at a given speed. Essential for gear selection and tire sizing.

Estimate 0-60 mph time from horsepower, vehicle weight, and drivetrain type. Compares against common performance benchmarks.

Estimate quarter-mile elapsed time and trap speed from vehicle weight and horsepower. Includes 1/8 mile estimates.

Calculate bolt pattern (PCD) from lug count and bolt-to-bolt measurement. Identify your wheel bolt pattern for 4, 5, 6, and 8 lug wheels.

Calculate power-to-weight ratio in HP/lb, HP/ton, kW/kg, and PS/kg. Compare against vehicle class benchmarks from economy cars to hypercars.

Convert between wheel offset (mm) and backspace (inches). Calculate poke or tuck when changing wheel width or offset.

Calculate static compression ratio from bore, stroke, chamber volume, head gasket, deck clearance, and piston dome or dish volume.

Calculate the ideal carburetor size in CFM from engine displacement, RPM, and volumetric efficiency. Recommends the nearest common carburetor size.

Calculate engine displacement from bore, stroke, and number of cylinders. Results in cc, cubic inches, and liters.

Calculate speedometer error after changing tire sizes. Find your actual speed vs. displayed speed and the percentage difference.

Calculate the right antifreeze-to-water ratio for your target freeze point. Shows how much coolant and water to mix for any cooling system capacity.

Calculate required fuel pump flow rate from target horsepower, BSFC, and fuel pressure. Recommends common pump sizes with pressure correction.

Calculate required fuel injector size from target horsepower, BSFC, number of injectors, and maximum duty cycle. Results in lb/hr and cc/min.

Calculate engine RPM at any vehicle speed from tire size, transmission gear ratio, and final drive ratio. Plan shift points and cruising RPM.

Convert between air/fuel ratio and lambda for gasoline, E85, methanol, and diesel. Includes target ranges for idle, cruise, and WOT.

Calculate the ideal spring rate from corner weight, motion ratio, and target ride frequency. Covers street, autocross, and race setups.

Calculate recommended exhaust pipe diameter and header primary tube size based on engine horsepower. Includes common size recommendations.

Calculate valve timing events, overlap, and cam character from duration at 0.050, lobe separation angle, and advance.

Estimate horsepower gain from turbo boost pressure. Enter naturally aspirated HP and boost PSI to calculate boosted output.

Calculate engine volumetric efficiency from displacement, RPM, and measured airflow. Supports MAF and MAP-based calculations.

Calculate mean piston speed from engine stroke and RPM. Results in ft/min, m/s, mph, and km/h with safety benchmarks for street, race, and extreme applications.

Calculate connecting rod ratio from rod length and stroke. Shows rod angle, piston dwell, acceleration characteristics, and comparisons to common engines.

Calculate air density, relative density, and density altitude from temperature, barometric pressure, and humidity. See how weather conditions affect engine power output.

Calculate weight transfer during acceleration from vehicle weight, wheelbase, CG height, and g-force. See dynamic axle loads for drag racing traction planning.

Calculate required turbo compressor size from target horsepower, boost pressure, and engine displacement. Shows airflow, pressure ratio, and suggested turbo frame.

Calculate dyno correction factors using SAE J1349, DIN 70020, and STD methods from temperature, barometric pressure, and humidity. Convert between corrected and observed HP.

Calculate intercooler size from target horsepower, boost pressure, and ambient temperature. Shows heat rejection, core volume, charge temperature drop, and density recovery.

Calculate ideal torque converter stall speed from peak torque RPM, vehicle weight, and use case. Shows recommended stall range, wheel torque, and launch force.