Mechanical advantage (MA) is a measure of the force amplification achieved by using a tool, mechanical device, or machine system. It is defined as the ratio of output force to input force, or equivalently, the ratio of input distance to output distance. A mechanical advantage greater than 1 means the machine multiplies the input force, making it easier to move heavy loads.

The concept is fundamental to understanding simple machines like levers, pulleys, inclined planes, wedges, screws, and wheel-and-axle systems. Engineers and physicists use mechanical advantage calculations to design efficient mechanical systems, from simple hand tools to complex industrial machinery.

The Ideal Mechanical Advantage (IMA) is calculated using the distance-based formula (d_in / d_out) and assumes no energy losses due to friction or other factors. The Actual Mechanical Advantage (AMA) is calculated using the force-based formula (F_out / F_in) and reflects real-world performance.

The efficiency of a machine is defined as the ratio of AMA to IMA, expressed as a percentage. Real machines always have efficiency less than 100% due to friction, deformation, and other energy losses. When designing mechanical systems, engineers must account for these losses to ensure adequate performance.