Mechanical advantage (MA) is the how much a machine multiplies the effort force put into it. The mechanical advantage can be calculated for the following simple machines by using the following formulas:
Lever: MA = length of effort arm / length of resistance arm.
Pulley: All pulleys have a fixed MA depending on the type. A pulley with one rope (single fixed pulley) has an MA = 1. A pulley with two ropes (single moveable pulley) has a MA = 2. A pulley with 6 ropes (block and tackle) has an MA = 4.
Wheel and Axle: MA = radius of wheel / radius of axle
Inclined Plane: MA = length of slope / height of slope
Most generally, the mechanical advantage is calculated thus:
MA = (the distance over which one must apply the force)/(the distance one wishes to move an object)
This requires an ideal simple machine, meaning that there are no losses due to Friction. This formula can be derived from the idea of conservation of energy.
Mechanical advantage can also be calculated using the laws of classical mechanics, especially the idea of torque.