Power-to-weight is often expressed at the maximum value, but the actual value may vary in use and variations will affect performance. The opposite of power-to-weight, the weight-to-power ratio or power loading is a ratio commonly applied to aircraft, cars, and vehicles in general to compare them.

Power-to-weight ratio is equal to thrust applied per unit mass multiplied by the velocity of a vehicle. The power to weight ratio is mathematically expressed as

Where

a(t) is acceleration of the center of mass of the body, changing with time.

V(t) is linear speed of the center of mass of the body.

g is the gravitational acceleration.