Set a price ceiling or floor and see whether it binds, the shortage or surplus, and who gains and loses.
Who this is for: Testing rent control or a minimum wage.
Market and control
The market
Demand schedule, two rows
Supply schedule, two rows
The control
Shortage or surplus, in units
4,000.00
Quantity demanded minus quantity supplied at the controlled price: a shortage under a ceiling, a surplus under a floor. Zero when the control does not bind.
Formula verified 27 September 2026
Does the control bind?
Yes: a shortage
A ceiling binds only below the market price; a floor only above it.
Quantity that still trades
15,000
The short side of the market sets it: what sellers supply under a ceiling, what buyers take under a floor.
Quantity demanded at the controlled price
19,000
Quantity supplied at the controlled price
15,000
Market price without the control
$600.00
Change in consumer surplus
$1,400,000.00
Buyers who still get the good pay less (or more, under a floor); buyers shut out lose theirs. Assumes the units go to the buyers who value them most.
Change in producer surplus
-$1,600,000.00
Sellers who still sell receive the controlled price; sellers shut out lose theirs.
Deadweight loss
$200,000.00
Gains from trade that no longer happen because fewer units change hands.
Prices, quantities and surplus before the control and under it. Surplus assumes the units go to the buyers who value them most and come from the lowest-cost sellers.
Without the control
With the control
Price
$600.00
$500.00
Quantity demanded
17,000
19,000
Quantity supplied
17,000
15,000
Quantity traded
17,000
15,000
Shortage
0
4,000
Consumer surplus
$7,225,000.00
$8,625,000.00
Producer surplus
$7,225,000.00
$5,625,000.00
Deadweight loss
$0.00
$200,000.00
Enter two rows of a demand and supply schedule, or the two equations. The default is OpenStax’s rent-control example: demand has risen, the market would clear at $600, and the city holds rent at $500. The results show how much still trades and the deadweight loss the control causes.
Calculated in your browser — the numbers you enter are never sent to our servers.
What it calculates: Shortage or surplus, in units, Does the control bind?, Quantity that still trades, Quantity demanded at the controlled price.
A $500 rent ceiling in a $600 market: 19,000 renters chasing 15,000 apartments
OpenStax tells the story in Table 3.7. Incomes rise, demand for rental housing shifts right, and the market would settle at $600 a month and 17,000 units. The city passes rent control at the old rent of $500. At that price landlords supply only 15,000 units, but 19,000 are wanted, so there is a shortage of 4,000.
The irony OpenStax points out is in the quantities: under the ceiling fewer apartments are rented (15,000) than at the market rent (17,000). The ceiling helps the renters who get one of the 15,000, and it shuts out the rest.
The calculator fits straight lines through the $500 and $600 rows of the table, which reproduces every figure above. Change the ceiling to see how the shortage grows as it falls further below $600, and how it vanishes at $600 and above, where the ceiling no longer binds.
FigureThe ceiling holds rent $100 below the market: 4,000 renters go without, 2,000 fewer apartments are rented than at $600, and $200,000 a month of trade disappears.
OpenStax Table 3.7
$500: 19,000 demanded, 15,000 supplied
$600: 17,000 demanded, 17,000 supplied
Ceiling at $500: 4,000 short
A ceiling binds only below the market price, and a floor only above it
A price ceiling is a legal maximum. Set above the market price, it changes nothing: the market clears at its own price, which is already under the limit. Only a ceiling below the market price binds, and then quantity demanded exceeds quantity supplied.
A price floor is a legal minimum, and it works the other way round. Below the market price it is harmless; above it, sellers offer more than buyers want and a surplus appears.
Under either kind, the short side of the market decides how much trades. Under a ceiling that is what sellers are willing to supply; under a floor, what buyers are willing to take. Nobody can be made to buy or sell more than they want to at the controlled price.
Who gains and who loses: renters who find an apartment gain $1.4 million a month, landlords lose $1.6 million, and $200,000 disappears
Consumer surplus is what buyers would have paid above what they do pay; producer surplus is what sellers receive above their cost. With the default rent ceiling, the renters who still get the 15,000 apartments pay $100 less a month, and consumer surplus rises by $1,400,000 a month even after counting the renters shut out. Producer surplus falls by $1,600,000.
DWL = ½ × (Q* − Q_traded) × (P_demand − P_supply at Q_traded)
The two do not cancel. The $200,000 difference is the deadweight loss: the 2,000 apartments that would have been rented at the market rent, and that renters valued more than landlords’ cost, are no longer rented at all. It is the triangle between the curves from 15,000 to 17,000 units, ½ × 2,000 × ($700 − $500).
The consumer-surplus gain assumes the apartments go to the renters who value them most. Where apartments go by luck, queueing or connections, some go to renters who value them less, and the true loss is larger than the triangle.
Rent ceiling, $ a month
Consumer surplus: +1,400,000
Producer surplus: −1,600,000
Deadweight loss: 200,000
A price floor works in reverse: a surplus, and a bill if the government buys it
Set the same market to a $700 floor and it runs backwards: sellers offer 19,000 units, buyers take 15,000, and 4,000 go unsold. OpenStax’s real example is European wheat, where price supports keep the price above the market level and the government buys the excess. If it buys the 4,000 units at $700, the bill is $2,800,000, and the calculator shows that cost when the control is a floor.
The best-known price floor is the minimum wage, a floor in the market for labor. The federal minimum has been $7.25 an hour since 2009, and many states set their own higher minimums. In the model, a binding wage floor means more people willing to work at that wage than jobs offered at it; how large that gap is in practice depends on how elastic labor demand is, which is an empirical question the straight-line model cannot settle.
What the straight-line model leaves out: queues, side payments and falling quality
A shortage has costs the triangle does not count. People spend time searching and queueing, landlords can demand side payments, and, as OpenStax notes, maintenance slips when landlords cannot raise rents: renters get cheaper housing and lower-quality housing at the same time.
Supply also responds more over time than it does at once. A ceiling that barely binds this year can produce a larger shortage later, as some apartments are converted to condominiums and fewer new ones are built.
This page and the Market Equilibrium Calculator run on one engine and answer one question each
The Market Equilibrium Calculator is the full supply-and-demand lab, with shifts, surplus shading and tax modules; its price-control module uses the same engine as this page, so the two always agree. This page is built around the control itself: schedule rows as input, the binding test, the shortage or surplus, the welfare transfer, and the government’s bill under a floor.
For the surplus areas on their own, the Consumer Surplus, Producer Surplus and Deadweight Loss calculators take one triangle at a time; for a tax instead of a control, the Tax Incidence Calculator splits the burden between buyers and sellers.
Frequently Asked Questions
What is the difference between a price ceiling and a price floor?
A price ceiling is a legal maximum price, such as rent control; a price floor is a legal minimum, such as the minimum wage or an agricultural price support.
When does a price ceiling cause a shortage?
Only when it is set below the market-clearing price. Then quantity demanded exceeds quantity supplied, and the gap is the shortage. A ceiling above the market price does nothing.
How do you calculate the shortage from a price ceiling?
Read the quantity demanded and the quantity supplied at the ceiling price and subtract: shortage = Qd − Qs. With OpenStax’s rent example, 19,000 − 15,000 = 4,000 units.
Why does a price ceiling create deadweight loss?
Fewer units trade than at the market price, and those lost trades were worth more to buyers than they cost sellers. The value of the trades that no longer happen is the deadweight loss.
Is the minimum wage a price floor?
Yes, in the labor market. If it is above the wage at which the market would clear, more people want to work at it than employers want to hire; how big that effect is depends on how responsive labor demand is.
Who benefits from a price ceiling?
The buyers who still manage to buy pay less and gain. Sellers lose, and buyers who are shut out lose the purchases they would have made. The total gain to the lucky buyers is smaller than the loss to sellers.
Sources & References
Figures on this page are checked against primary, authoritative sources. Links open in a new tab.
Demand and supply are straight lines through the two rows (or the equations) you enter.
Under a shortage, the units go to the buyers who value them most; under a surplus, they come from the sellers with the lowest costs. Real rationing is less tidy, so the deadweight loss shown is a floor.
The control is enforced: no side payments or black market.
Where it stops
The surplus levels extrapolate the straight lines all the way to zero quantity; the changes and the deadweight loss depend only on the part of the curves near the market price and are more robust.
Queues, search costs, falling quality and black markets are real costs of controls that the triangle does not count.
Short-run and long-run supply differ: a rent ceiling’s shortage usually grows as landlords convert or stop maintaining units.
Related Calculators
Market EquilibriumSolve equilibrium price and quantity from linear demand and supply, with surplus, a shift simulator, and tax incidence.
Deadweight LossSize the welfare triangle a per-unit tax destroys, alongside the tax revenue it actually raises.
Consumer SurplusFind the value buyers gain above what they pay, from the choke price, market price, and quantity sold.
Producer SurplusFind the value sellers gain above their minimum acceptable price, from the market price and quantity sold.
Tax IncidenceHow a per-unit tax splits between buyers and sellers, the prices each faces, the revenue and the deadweight loss, with the elasticity route to the same split.
Opportunity CostCompare two choices to see net value, opportunity cost, explicit vs implicit costs, and risk-adjusted scenarios.
Comparative AdvantageFind comparative and absolute advantage between two producers and two goods, plus the mutually beneficial trade range.
GDPGross domestic product by the expenditure method (C + I + G + NX) or the income method — wages, rent, interest, profit, taxes and depreciation.
Sudha, J. (2026, September 27). Price Ceiling and Floor Calculator. Calculator Matters. https://calculatormatters.com/economics/price-ceiling-floor-calculator/
Published the price ceiling and floor calculator: from two schedule rows or the equations, whether a control binds, the shortage or surplus, what still trades, the change in consumer and producer surplus, the deadweight loss, and the government’s bill if it buys a floor’s surplus.
Runs on the Market Equilibrium Calculator’s engine; checked against OpenStax’s rent-control example (Table 3.7: a $500 ceiling, 15,000 supplied against 19,000 demanded) and against the deadweight-loss triangle in 3,000 random markets.
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