Marginal Utility vs Total Utility

Marginal utility is the additional satisfaction gained from consuming one more unit of a good.

It typically falls as you consume more of a good, a pattern called diminishing marginal utility. Consumers compare marginal utility per dollar across goods to allocate spending. When marginal utility is negative, consuming more actually reduces total utility.

Total utility is the overall satisfaction a consumer receives from consuming a given quantity of a good.

It rises as long as marginal utility is positive and is maximized when marginal utility equals zero. Total utility equals the sum of the marginal utilities of all units consumed. Beyond the satiation point it falls.