Marginal Cost (MC) = Change in Total Cost ÷ Change in Quantity
MC = ΔTC ÷ ΔQ
Marginal Benefit (MB) = Change in Total Benefit ÷ Change in Quantity
MB = ΔTB ÷ ΔQ
Identify the initial total cost or total benefit
Identify the new total cost or total benefit after producing or consuming one more unit
Subtract the initial value from the new value
Divide the result by the change in quantity
For one additional unit, the change in quantity is usually 1
Marginal Cost = Cost of producing one more unit
Marginal Benefit = Benefit gained from consuming one more unit