The actual mechanical advantage (AMA) is a computed value based on measuring both the input and output forces. Actual mechanical advantage differs from ideal mechanical advantage (IMA) because it takes into account energy losses from a variety of factors such as deflection, deformation, friction, and wear.
The AMA of any machine is calculated as the ratio of the measured force output to the measured force input:
AMA = `F_"Out"` / `(F_"In")`
Not that the ratio of the experimentally determined mechanical advantage to the ideal mechanical advantage is the efficiency `eta` of the machine:
`"eta" = "AMA"/"IMA"`