Identify the input whose marginal product you want to find
Hold all other inputs constant
Calculate total output with one unit of the input
Calculate total output with one fewer unit of the input
Subtract the lower output from the higher output
Divide the change in output by the change in input
Use the formula: Marginal Product = Change in Total Output / Change in Input
For one additional unit, this is often: MP = Q(n) – Q(n-1)