Marginal utility of a commodity to a consumer is the extra utility which he gets when he consumes one more unit of the commodity. It can be defined as the utility derived from the marginal or the last unit consumed. More precisely, Marginal Utility (MU) is the change in the total utility resulting from the consumption of one additional unit. That is,
MU = ∆TU/∆C
Where ∆TU = change in total utility, and ∆C = change in consumption by one unit
Marginal unit (MU) may also be expressed as
MU = TUn – Tn-1
Where TUn = total utility derived from the consumption of n units and TUn-1 = total utility derived from the consumption of n – 1 units.