Equilibrium price is the modeled price where quantity demanded equals quantity supplied, leaving neither excess demand nor excess supply.
The equilibrium price is the price at which quantity demanded equals quantity supplied in a defined market and period, given the model’s assumptions. It is also called the market-clearing price because the model has neither excess demand nor excess supply at that price.
Equilibrium is a benchmark, not a guarantee that every market instantly settles at one price. It also does not mean the outcome maximizes a seller’s profit, is fair to every participant, or equals an asset’s intrinsic value.
Let demand be Q_d(P) and supply be Q_s(P). The equilibrium price P* solves:
The equilibrium quantity is then:
Both values need units. A result such as “price 25, quantity 400” is incomplete unless the analysis states the currency, unit of product, market boundary, and time period.
Assume a hypothetical market has these schedules:
Set quantity demanded equal to quantity supplied:
Substitute the price into either schedule:
The modeled equilibrium is $15 per unit and 105 units per period.
| Market price | Quantity demanded | Quantity supplied | Difference |
|---|---|---|---|
$12 | 120 | 90 | Excess demand of 30 |
$15 | 105 | 105 | Equilibrium |
$18 | 90 | 120 | Excess supply of 30 |
The schedules are invented for instruction. An empirical estimate would require data and assumptions about market boundaries, curve shape, omitted factors, and timing.
In a flexible competitive market, imbalance creates incentives to adjust:
Adjustment can occur through quantity, waiting time, quality, eligibility, search, or inventory rather than price alone. The simple model is most useful when those other channels are identified rather than ignored.
An observed price can differ from a theoretical equilibrium for several reasons:
| Price concept | What it represents |
|---|---|
| Equilibrium price | Model solution where aggregate quantity demanded equals aggregate quantity supplied |
| Transaction price | Price of a completed exchange at a particular time and size |
| Bid price | Highest displayed or available buying interest under stated market conditions |
| Ask price | Lowest displayed or available selling interest under stated market conditions |
| Administered price | Price set by a government, regulator, contract, or organization |
| Estimated value | Analyst’s conclusion based on cash flows, comparables, costs, or another valuation method |
A thinly traded asset may have stale quotes and no recent transaction. A large order can execute across several prices. A regulated utility price can be deliberately set through a rate process rather than continuous market clearing. One observed number should not be assigned every meaning in the table.
Suppose the example’s demand increases from Q_d = 180 - 5P to:
Supply remains Q_s = 30 + 5P. The new solution is:
The market does not merely “return” to the old $15 equilibrium. The demand shift changes the model itself, producing a new equilibrium price and quantity.
Comparative statics compares the initial equilibrium with the new one after a change, while abstracting from the adjustment path.
| Curve change | Price direction | Quantity direction |
|---|---|---|
| Demand shifts right | Up | Up |
| Demand shifts left | Down | Down |
| Supply shifts right | Down | Up |
| Supply shifts left | Up | Down |
| Demand and supply both shift right | Ambiguous | Up |
| Demand shifts right and supply shifts left | Up | Ambiguous |
“Ambiguous” means the direction depends on relative shift sizes and curve slopes. It does not mean the model has no answer once those inputs are known.
The original version of this page incorrectly described equilibrium price as the price that maximizes a manufacturer’s profit. These are different concepts.
A firm’s profit is:
Under a standard differentiable model, a profit-maximizing firm chooses output where marginal revenue equals marginal cost, subject to constraints:
In perfect competition, an individual firm treats market price as given and chooses its own output. Market equilibrium then coordinates aggregate supply and demand. A monopolist instead recognizes that selling more may require a lower price and chooses price-output combinations differently.
Equilibrium can exist at a price that leaves some firms with losses, induces exit later, or changes when costs and entry respond. Market equilibrium and maximum industry profit are not interchangeable.
For financial assets, the equilibrium concept helps organize price formation, but the market can update continuously as information and expectations change.
Market structure matters. Dealer inventory, bid-ask spreads, tick sizes, auction rules, hidden orders, settlement, and trading halts can affect the observed clearing process.
A price ceiling is binding only when set below the otherwise applicable equilibrium price. In the basic model, it produces excess demand. A price floor is binding only when set above equilibrium and produces excess supply.
If a ceiling is above equilibrium or a floor is below it, the control is nonbinding at the initial conditions. Stating that a control exists is therefore insufficient; compare it with the relevant equilibrium benchmark.
An equilibrium model can still be useful in these settings, but its assumptions and omitted mechanisms should be explicit.
OpenStax’s Changes in Equilibrium Price and Quantity explains equilibrium and comparative statics. Its discussion of the market system and price information applies the model across goods, labor, and financial capital. The SEC’s Investor.gov bid and ask definition distinguishes the two quoted prices in securities markets.
This article provides general economics and financial education, not investment advice, valuation advice, or a price forecast. An estimated equilibrium depends on model structure, data, assumptions, and market institutions.