What is the consumer surplus?
Type the market price, the quantity sold, and the highest price a buyer would pay. The consumer surplus calculator gives the consumer surplus, and with the lowest price a seller would accept, the producer surplus and the social surplus too.
- Consumer surplus
- $560.00
Consumer surplus is $560.00.
- Producer surplus
- $560.00
- Social surplus
- $1,120.00
- Consumer surplus per unit
- $20.00
Consumer surplus: $560.00. Consumer surplus is $560.00.
The results are estimates for information only. They are not financial, tax, or legal advice. Check the numbers with your lender or a qualified professional before you decide. Terms of use
How to calculate
Computes consumer surplus and producer surplus from the market price and quantity with straight-line demand and supply, or for single purchases, with total social surplus.
Example with the default inputs (Market Demand and supply lines, Market price $80.00, Quantity sold 28, Highest price a buyer would pay $120.00, Lowest price a seller would accept $40.00): Consumer surplus is $560.00.
Method: Lines: CS = ½ × Q × (highest price − P), PS = ½ × Q × (P − lowest price). Same value per unit: CS = Q × (highest price − P), PS = Q × (P − lowest price). Social surplus = CS + PS.
- Lines mode: demand and supply are straight lines through the market point, so each surplus is a triangle.
- Same value per unit: every unit is worth the same to the buyer and costs the same to the seller.
Worked examples
Each example is checked against the calculator on every build.
- Market Demand and supply lines, Market price $80.00, Quantity sold 28, Highest price a buyer would pay $120.00, Lowest price a seller would accept $40.00 gives Consumer surplus $560.00, Producer surplus $560.00, Social surplus $1,120.00, Consumer surplus per unit $20.00.Source: https://openstax.org/books/principles-economics-3e/pages/3-5-demand-supply-and-efficiency
- Market Same value per unit, Market price $30.00, Quantity sold 1, Highest price a buyer would pay $45.00, Lowest price a seller would accept $18.00 gives Consumer surplus $15.00, Producer surplus $12.00, Social surplus $27.00.Source: https://openstax.org/books/principles-economics-3e/pages/3-5-demand-supply-and-efficiency
- Market Demand and supply lines, Market price $10.00, Quantity sold 100, Highest price a buyer would pay $30.00 gives Consumer surplus $1,000.00, Consumer surplus per unit $10.00.Source: https://openstax.org/books/principles-economics-3e/pages/3-5-demand-supply-and-efficiency
How it works
OpenStax defines consumer surplus as what buyers would have been willing to pay minus what they actually paid, and producer surplus as the price producers received minus the price they would have been willing to accept. Social surplus is their sum. The page measures them in one of two ways.
Demand and supply lines (default). Demand and supply are straight lines through the market point (quantity Q at price P). The demand line reaches the price axis at the highest price a buyer would pay, P_max; the supply line reaches it at the lowest price a seller would accept, P_min. Each surplus is a triangle with base Q:
- Consumer surplus = ½ × Q × (P_max − P).
- Producer surplus = ½ × Q × (P − P_min).
- Social surplus = consumer surplus + producer surplus.
- Consumer surplus per unit = ½ × (P_max − P).
Same value per unit. Every unit is worth P_max to the buyer and costs the seller P_min (one buyer, or identical buyers). Each surplus is a rectangle:
- Consumer surplus = Q × (P_max − P).
- Producer surplus = Q × (P − P_min).
- Social surplus = consumer surplus + producer surplus; per unit = P_max − P.
Rules. Prices and the quantity are 0 or more. P_max below P gives no answer (nobody buys); P_min above P gives no answer (nobody sells). P_min is optional; without it there is no producer or social surplus. With Q = 0 the per-unit value is not shown.
Rounding. Every value is an exact fraction of the typed decimals; money shows to the cent, rounded half up.
Worked examples by hand
Tablets (page default). P = $80, Q = 28, P_max = $120, P_min = $40 (the market point is OpenStax's; the two intercepts are assumed). Consumer surplus = ½ × 28 × (120 − 80) = $560.00. Producer surplus = ½ × 28 × (80 − 40) = $560.00. Social surplus = $1,120.00. Per unit = ½ × 40 = $20.00.
One ticket. Same value per unit: P = $30, Q = 1, P_max = $45, P_min = $18. Consumer surplus = 1 × (45 − 30) = $15.00. Producer surplus = 1 × (30 − 18) = $12.00. Social surplus = $27.00.
Consumer surplus only. P = $10, Q = 100, P_max = $30. Consumer surplus = ½ × 100 × 20 = $1,000.00; per unit $10.00.
Other questions people ask
How do I calculate consumer surplus?
With a straight-line demand curve, consumer surplus is the triangle between the demand line and the market price: ½ × quantity × (highest price buyers would pay − market price). At $80 and 28 units, with demand reaching 0 at $120: ½ × 28 × 40 = $560.
How do I calculate producer surplus?
With a straight-line supply curve, producer surplus is the triangle between the market price and the supply line: ½ × quantity × (market price − lowest price a seller would accept). At $80 and 28 units, with supply starting at $40: ½ × 28 × 40 = $560.
What is consumer surplus for a single purchase?
The most you would have paid minus what you paid. If you would pay $45 for a ticket and buy it for $30, your consumer surplus is $15. Choose “Same value per unit” for this case.
What is social surplus?
Consumer surplus plus producer surplus: the total gain to buyers and sellers from trading. OpenStax calls a market efficient when it produces the quantity that makes social surplus as large as possible.
Where do the highest and lowest prices come from?
They are where the demand and supply lines meet the price axis. If demand is P = 120 − 2Q, the highest price is $120; if supply is P = 40 + Q, the lowest price is $40. Read them from your graph or equations.
Can consumer surplus be negative?
No. If the market price is above the highest price any buyer would pay, nobody buys, and the page gives no answer.