Consumer and Producer Surplus Formula
Reference for consumer and producer surplus formulas.
Covers how market price affects buyer and seller gains in supply and demand equilibrium analysis.
Need to calculate, not just reference? Use the interactive version.
Open Consumer Surplus Calculator →
Key Notes
- Definition: Consumer surplus is the difference between what a buyer is willing to pay and what they actually pay. Graphically, it is the area below the demand curve and above the market price — typically a triangle when the demand curve is linear.
- Triangle formula: CS = ½ × Q* × (P_max − P*): P_max is the maximum willingness-to-pay (demand intercept), P* is the equilibrium price, and Q* is the equilibrium quantity. This assumes a straight-line demand curve.
- Demand elasticity determines surplus size: Inelastic demand (steep curve) creates large consumer surplus at any given price. Elastic demand (flat curve) creates small surplus. Free services (P = 0) generate maximum consumer surplus equal to the entire area under the demand curve.
- Deadweight loss: Taxes, price floors, or monopoly pricing raise price above equilibrium. Some consumer surplus is transferred to the seller (producer surplus) and some is destroyed entirely — this destroyed value is the deadweight loss.
- Applications: Consumer surplus is used in welfare economics to evaluate the total benefit of markets, in cost-benefit analysis of public goods, in auction design theory, and in pricing strategy (a firm extracting all CS through price discrimination earns maximum revenue).