Engine
Engine Displacement Calculator
Engine capacity from bore, stroke and cylinder count, in cc, litres and cubic inches.
V = π/4 × bore² × stroke × cylinders
Also called engine size calculator · cc calculator
Engineering · 9 calculators
Engine Calculators
Engine displacement from bore and stroke, compression ratio, horsepower and torque, piston speed and airflow.
Engine
Compression Ratio Calculator
Static compression ratio from swept and clearance volume, with the head gasket contribution.
CR = (swept + clearance) ÷ clearance
Also called static compression ratio · cr calculator
Engine
Horsepower Calculator
Horsepower from torque and RPM, from watts, or from the quarter-mile trap speed.
P (W) = τ × 2π × RPM / 60
Also called hp calculator · torque to hp
Engine
Torque Calculator
Torque from force and lever arm (τ = F·r), solving for any variable, in N·m and lb·ft.
τ = F × r × sin θ (θ = 90° for maximum to…
Also called torque formula · moment of force
Engine
RPM Calculator
Convert between RPM, surface speed and angular velocity for shafts, wheels and tools.
surface speed = π × d × RPM
Also called revolutions per minute · rpm to rad/s
Engine
Piston Speed Calculator
Mean piston speed at a given RPM — the key indicator of engine stress and longevity.
mean piston speed = 2 × stroke × RPM / 60
Also called mean piston speed · piston velocity
Engine
Engine Airflow Calculator
Airflow an engine needs in CFM from displacement, RPM and volumetric efficiency.
CFM = displacement × RPM × VE ÷ 2 (four s…
Also called cfm calculator engine · intake airflow
Engine
Fuel Consumption Calculator
Fuel consumption from distance and fuel used, in L/100km, km/L and MPG, plus the cost.
L/100km = litres used ÷ distance × 100
Also called fuel efficiency calculator · litres per 100 km
Engine
Power to Weight Ratio Calculator
Power-to-weight ratio in hp/tonne and W/kg, with an estimated 0–100 km/h time.
ratio = power ÷ total weight
Also called hp per ton · w/kg calculator
Key engine formulas
| Engine Displacement | V = π/4 × bore² × stroke × cylinders |
|---|---|
| Compression Ratio | CR = (swept + clearance) ÷ clearance |
| Horsepower | P (W) = τ × 2π × RPM / 60 · 1 hp = 745.7 W |
| Torque | τ = F × r × sin θ (θ = 90° for maximum torque) |
| RPM | surface speed = π × d × RPM · ω = 2π × RPM / 60 |
| Piston Speed | mean piston speed = 2 × stroke × RPM / 60 |
| Engine Airflow | CFM = displacement × RPM × VE ÷ 2 (four stroke) |
| Fuel Consumption | L/100km = litres used ÷ distance × 100 |
| Power to Weight Ratio | ratio = power ÷ total weight |
Engine questions
What is the difference between hp and PS?
Metric horsepower (PS or CV) is 735.5 W, about 1.4% smaller than the 745.7 W mechanical horsepower.