Mechanical devices that change the direction or the magnitude of the force that is applied is called as the simple machines. The measure of the energy saved by using these simple machines is called as the mechanical advantage. Six basic simple machines as defined by the Renaissance scientists are Lever, wheel and axle, pulley, inclined plane, wedge and screw.
In general, the ratio of the output to the input force is called as mechanical advantage. Here you can find a list of calculators that calculates the mechanical advantage of these simple machines