The indicated power of a four-stroke engine (in watts) is equal to (where P = Mean effective pressure in N/m2, L = Length of stroke in metres, A = Cross-sectional area of the piston in m2, and N = Speed of the engine in revolutions per second (r.p.s))

• P.L.A.N/2
• P.L.A.N
• 2 x P.L.A.N
• P.L.A.N/4