Price vs ATC: Calculate Economic Profit or Loss

The same output rule can produce profit, break-even, or loss.

Compare Three Competitive-Firm Cases

These cases concern a price-taking firm, an output on the relevant rising MC branch, and fixed economic costs unavoidable during the stated period. The operating quantity must be a global best choice, not just any MC intersection. ATC includes the relevant explicit and implicit opportunity costs. The standard shutdown comparison assumes no omitted operating-only fee.

Read ATC at the Chosen Quantity

Read ATC at the firm’s globally best positive output, then compare operating profit with the zero-output payoff. An ATC value at a different quantity does not determine the chosen profit rectangle. The cases below retain their supplied graph values; the later quadratic-cost model is a separate independent example.

Use Price and ATC to Identify the Sign

If P>ATC at the chosen positive quantity, the profit rectangle is (P-ATC)q. If P=ATC, economic profit is zero. With AVC≤ P<ATC, operation can minimize a loss: strictly above AVC it contributes toward unavoidable fixed cost, while equality with AVC gives the same payoff as shutdown. With P<AVC at the best operating candidate, shut down rather than accept the larger operating loss. Do not mistake the equality case for a unique requirement to operate.

Measure the Right Rectangle

For the usual smooth competitive model, read the cost curves at the relevant P=MC output after checking global optimality and shutdown. Price may be above ATC at one quantity and below it at another. Only the chosen operating quantity defines the rectangle: its width is firm output, and its signed height is price minus ATC. Use a negative number for profit during a loss or a positive magnitude labelled loss.

Separate Profit from Producer Surplus

With economic variable and fixed costs defined consistently, producer surplus is revenue minus variable cost, whereas economic profit is revenue minus total economic cost. Their difference is unavoidable fixed economic cost in this benchmark. Producer surplus can be positive while economic profit is negative, because operating covers variable cost but falls short of total cost.

Check the Supplied Loss Example

Market price is $14. Rising MC equals $14 at 60 units. AVC is $10 and ATC is $16. The firm produces 60 because price covers AVC. Its loss is (16-14)60=$120, smaller than the fixed-cost loss from shutdown.

Cross-Check Revenue and Cost Totals

At that output, revenue is $840, variable cost is $600, and total cost is $960. Producer surplus is $240. Fixed cost is 960-600=$360. Profit is 240-360=-$120. The three totals confirm both operation and loss.

Read the Operating Reference Table

Interpret Normal Economic Profit

At break-even, revenue covers variable cost and unavoidable fixed economic opportunity costs. Producer surplus therefore equals fixed economic cost while economic profit is zero. That is a normal-return outcome in the economic-cost convention; it is not a statement that the owner receives no payment or that accounting profit must also be zero.

Keep the Time Horizon Explicit

Persistent revenue insufficient to cover the relevant economic costs can induce exit once the firm can avoid those costs by leaving. The short-run table concerns an operating decision before all inputs can adjust. A temporary loss, by itself, does not establish either immediate shutdown or a fixed date for exit; consider avoidability and the stated horizon.

Report Loss Magnitudes Consistently

When price is below ATC, either report loss as the positive magnitude (ATC-P)q or report profit as the negative number (P-ATC)q. Mixing the two conventions creates sign errors. The shaded loss rectangle has height ATC-P and width firm output.

Check Why Break-Even Can Favor Operation

If the chosen break-even quantity has price strictly above AVC and positive unavoidable fixed cost, producing is strictly better than shutting down: operation earns zero economic profit, while shutdown loses that fixed cost. If fixed cost is zero, ATC and AVC can coincide and this strict preference need not hold. Keep the boundary assumptions attached to the conclusion.

Make the Two Profit Formulas Agree

If totals are supplied, profit is TR-TC. If price, ATC, and output are supplied, use the rectangle. The methods must agree. Multiplying price minus MC by output incorrectly treats the last unit’s cost as the average cost of every unit.

Check Accounting and Opportunity Costs

A separate accounting illustration makes the distinction concrete. Suppose expected revenue is $900, explicit costs are $780 and additional relevant opportunity costs are $120. Accounting profit is $120, but economic profit is zero after subtracting the opportunity cost. These are hypothetical totals; they do not describe a product’s price, actual business results or a promised return.

Ask Two Different Cost Questions

Use two separate questions: does operation improve on the shutdown payoff, and does operation cover all relevant economic costs? An answer can be yes to the first and no to the second. The original loss example and the independent three-price schedule below show both comparisons numerically.

Read the Profit and Shutdown Explanation

OpenStax’s competitive output lesson discusses revenue, total cost, average cost and the shutdown comparison. The separate quadratic-cost model and questions below are original hypothetical teaching material rather than copied textbook exercises or figures.

Compare Three Prices with the Same Costs

Let output q be continuous and nonnegative. One price-taking firm has total economic cost TC = 0.5q² + 72, variable cost VC = 0.5q² and unavoidable fixed economic cost of $72 per period. Marginal cost is MC = q. For positive q, AVC = 0.5q and ATC = 0.5q + 72/q. Thus the operating choice is q = P for each positive price in the table.

At price $16, the firm chooses sixteen units, earns revenue of $256 and incurs variable cost of $128. Total economic cost is $200 after including the $72 fixed cost. Profit is therefore $56, equal to the rectangle (16 − 12.50) × 16. Producer surplus is $128; subtracting the fixed economic cost converts that figure into profit.

At price $12, output is twelve, revenue is $144, variable cost is $72 and total cost is $144. Economic profit is zero, but producer surplus is $72. Minimum ATC occurs at this same output: ATC − 12 = (q − 12)²/(2q), which is nonnegative for every positive q. At price $8, output eight gives $64 revenue and $104 total cost, hence a $40 loss. It still improves on the $72 shutdown loss because variable cost is only $32.

The operating choices are global optima. Profit can be written as 0.5P² − 72 − 0.5(q − P)². At each positive price, the squared term is minimized at q = P, and the resulting profit exceeds the −$72 shutdown payoff. The different profit signs therefore arise with the same MC rule; they are not evidence that the output choice should move to an arbitrary minimum-cost point.

Verify the Original Loss Example

Can the supplied price of $14, output of sixty, AVC of $10 and ATC of $16 describe a consistent globally optimal operating decision?

Try Three Price and ATC Questions

Connect Profit with Supply and Market Price

Review the short-run supply and shutdown rule, trace market price into a firm graph, or continue with the CLEP Microeconomics learning hub.