Shutdown Point vs Break-Even Point: Min AVC vs Min ATC

The break-even point is the price equal to minimum ATC, where a firm earns zero economic profit. The shutdown point is the price equal to minimum AVC: if price falls below it, the firm produces nothing in the short run. Between the two, the firm takes a loss but keeps producing, because its revenue covers all of its variable cost and part of its fixed cost.

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A perfectly competitive market and one price-taking firm earning a short-run profit. Tap it to drag the curves, open the full version, or put it on your own site free, or turn it into a five-minute class activity.

These two thresholds organize almost every short-run decision in the perfect competition unit. This guide defines both, finds them in a cost table, runs four prices through the table, builds the firm's short-run supply curve, and then shows how the long-run exit decision differs. The glossary entries for the shutdown point and the break-even point give the short definitions.

The two thresholds

Both points sit on the marginal cost curve, because MC crosses each average cost curve at its minimum.

Break-even point: P = minimum ATC. At this price, total revenue equals total cost, so economic profit is zero. Above it the firm earns profit. Below it the firm takes a loss. Zero economic profit still includes a normal return to the owner, since ATC counts opportunity costs. The economic profit vs accounting profit guide explains why.

Shutdown point: P = minimum AVC. At this price, total revenue just equals total variable cost. Below it, producing loses more than closing. The break-even point vs shutdown point comparison puts the two definitions next to each other.

Why compare price with AVC and not ATC for the shutdown decision? In the short run, fixed costs are paid whether the firm produces or not. Closing the doors does not cancel the lease. A cost the firm cannot avoid cannot change its decision, so only variable costs matter for "produce or not this period." The ATC vs AVC comparison shows how far apart the two curves sit at different outputs.

A cost table with both points

A small furniture workshop in a perfectly competitive market has a total fixed cost of $40 per day. Q is chairs per day.

MC is the change in total cost from one more chair, AVC = TVC / Q, and ATC = TC / Q.

• Minimum AVC is $15, at 4 chairs. The shutdown price is $15.
• Minimum ATC is $24, at 5 chairs. The break-even price is $24.

Notice that MC equals AVC for the first chair ($20), sits below AVC for the second through fourth chairs and above it from the fifth, and MC is below ATC up to the fifth chair and above it from the sixth. In a table the crossing happens between rows; on a smooth graph MC passes through each curve exactly at its lowest point.

Four prices, four decisions

A price taker keeps adding chairs along the rising part of MC until the next chair would cost more than the price, as long as the price covers AVC at that output.

Price $30: profit. The sixth chair costs $28 and the seventh costs $39, so the workshop makes 6. Total revenue is 30 x 6 = $180, total cost is $148, and profit is $32. Price is above the $24 break-even point.

Price $24: break even. The fifth chair costs $20 and the sixth costs $28, so it makes 5. Total revenue is 24 x 5 = $120, which equals total cost of $120. Economic profit is zero.

Price $18: loss, but keep producing. The fourth chair costs $12 and the fifth costs $20, so it makes 4. Total revenue is 18 x 4 = $72 and total cost is $100, a loss of $28. Shutting down would mean a loss of the full $40 fixed cost. Producing is better by $12.

Check it per unit. Each chair sells for $18 and costs $15 in variable cost on average, so 18 - 15 = $3 per chair goes toward fixed cost. Four chairs cover 3 x 4 = $12 of the $40, leaving 40 - 12 = $28 uncovered, which matches the loss.

Price $12: shut down. Below the $15 shutdown point, every output loses more than $40. At 4 chairs, revenue is 12 x 4 = $48, total variable cost is $60, and the loss is 100 - 48 = $52. At 1 chair the loss is 60 - 12 = $48. Closing loses $40, so the workshop produces nothing.

At exactly $15, producing 4 chairs brings in $60, which equals TVC, so the loss is $40 either way and the firm is indifferent. You can rerun these tests with your own numbers in the shutdown point calculator and the break-even point calculator.

The loss-minimizing range

Any price between minimum AVC and minimum ATC puts the firm in the middle case: losing money, but losing less by producing. On a graph, the price line sits below ATC and above AVC at the MR = MC quantity. The loss rectangle has height ATC minus P, and it is smaller than the total fixed cost the firm would lose by closing.

This is the case that surprises students most. A firm with a loss is not automatically a firm that should close. The profit, break even and loss explainer walks through reading all three cases off the side-by-side graphs.

The short-run supply curve is MC above minimum AVC

Since the firm produces where P = MC whenever P is at least minimum AVC, and produces nothing below it, its short-run supply curve is the MC curve above minimum AVC. Reading the table:

Below the shutdown point, the supply curve sits on the vertical axis at zero output. The market's short-run supply curve is the horizontal sum of these firm curves. You can move the market price and watch the firm's choice change in the perfect competition sandbox.

The long run: exit below minimum ATC

In the long run, there are no fixed costs. The lease ends, the equipment can be sold, and leaving the industry costs nothing. So the long-run test compares price with ATC: a firm exits if price stays below minimum ATC.

At $18 the workshop keeps producing today but exits once its commitments run out, because staying means a $28 loss every day and leaving means a loss of zero. At $30 it stays, and its profit attracts new firms.

In a perfectly competitive market, entry and exit push the price toward minimum ATC. So the break-even point does double duty: it is the short-run zero-profit price and the long-run equilibrium price. The short run vs long run guide covers the difference between shutting down and exiting in more depth.

How it shows up on the AP exam

This material is AP Micro topic 3.6. Students are usually asked to:

• Identify the shutdown price or the break-even price from a graph or a cost table.
• Decide whether a firm should produce at a given price, and explain why.
• Calculate profit or loss at a given price, or the loss if the firm shuts down.
• Identify the firm's short-run supply curve.
• Explain what happens in the long run if firms are taking losses.

Common mistakes:

• Using ATC for the shutdown decision. The short-run test compares price with AVC.
• Saying a firm with a loss should shut down. If P is above AVC, producing loses less.
• Saying the loss from shutting down is zero. In the short run it equals total fixed cost.
• Treating break even as zero accounting profit. It is zero economic profit, which includes a normal return.
• Mixing up shutdown and exit. Shutdown is temporary and short run. Exit means leaving the industry, and it shifts market supply left.

For the full context, see the perfect competition guide and the AP Micro 3.6 topic page.