Consumer Surplus Calculator

Calculate consumer surplus — the economic benefit buyers receive when they pay less than their maximum willingness to pay — using a linear demand curve.

By AbraCalc Editorial Team · Reviewed by AbraCalc Methodology Review · Last reviewed: 2026-06-25

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How to use this tool

Enter maximum willingness to pay (demand intercept), actual market price and quantity demanded at market price in the fields above.
Results update instantly as you type — or click Calculate.
Read your consumer surplus and the full breakdown beneath it.

Formula

CS = ½ × (P_max − P_market) × Q

Where CS = consumer surplus, P_max = maximum willingness to pay (demand curve intercept), P_market = actual market price, Q = quantity demanded at the market price.

How it works

Consumer surplus is the area of the triangle above the market price and below the linear demand curve. With a straight-line demand curve, this area equals one-half times the base (quantity demanded) times the height (the gap between the demand intercept and the market price).

This model assumes a linear (straight-line) demand curve. For non-linear demand curves, surplus must be computed by integrating the demand function. Producer surplus and total welfare are not calculated here.

Worked example

Demand intercept $100, market price $60, quantity 40

Maximum willingness to pay P_max = $100, market price P = $60, quantity Q = 40 units.
Price gap = $100 − $60 = $40.
Consumer surplus = 0.5 × $40 × 40 = $800.
Total consumer expenditure = $60 × 40 = $2,400.

Consumer surplus = $800.

Key terms

Consumer Surplus: The difference between what consumers are willing to pay for a good and what they actually pay, representing their net economic benefit from a transaction.
Willingness to Pay: The maximum price a buyer would accept paying for a good or service before preferring not to purchase it.
Demand Curve Intercept: The price at which quantity demanded falls to zero; the highest price any consumer in the market is willing to pay.
Linear Demand Curve: A straight-line relationship between price and quantity demanded, which gives a triangular area for consumer surplus.
Market Price: The equilibrium price at which goods are actually bought and sold in the market.