What is the common formula for calculating the efficiency of a simple machine?

The common formula for calculating the efficiency of a simple machine is based on the relationship between the work done by the machine and the work put into it. Efficiency is defined specifically as the ratio of useful output work to the input work, expressed as a percentage. This is formulated as (Output Work / Input Work) x 100%.

In practical terms, this means that to determine how effectively a simple machine is converting the energy or work provided to it, one compares the amount of work that the machine outputs (useful work done) against the work put into the machine. An efficiency greater than 100% is not possible, as that would suggest that the machine is generating more energy than is inputted, which violates the law of conservation of energy. Therefore, this formula provides a clear and concise way to assess the performance of a simple machine in its intended function.