Average Fixed Cost (AFC) is a firm's total fixed cost divided by the quantity of output produced. Because fixed costs don't change with output, AFC always falls as quantity rises, spreading the same fixed expense over more units.
Average Fixed Cost (AFC) tells you how much fixed cost each unit of output carries. The formula is simple: AFC = Total Fixed Cost ÷ Quantity. Fixed costs are the bills that stay the same no matter how much you make (rent, insurance, a loan payment), so as you crank out more units, that same lump of cost gets split across more and more of them.
Here's the key behavior: AFC always declines as output increases. Think of it like splitting a $100 pizza bill. With 2 people it's $50 each, with 10 people it's $10 each. Same bill, smaller share per person. That's why the AFC curve slopes steadily downward and never turns back up. This is strictly a short-run idea, because fixed costs only exist in the short run. In the long run (EK PRD-1.A.9), firms can adjust every input, so all costs become variable and AFC disappears as a separate concept.
AFC lives in Unit 3 (Production, Cost, and the Perfect Competition Model), specifically Topic 3.3, and it's part of the family of cost curves you define, graph, and calculate under learning objectives AP Micro 3.3.A, 3.3.B, and 3.3.C. You won't usually be asked about AFC in isolation. Its real job is explaining the shape of other curves. The vertical gap between Average Total Cost and Average Variable Cost IS Average Fixed Cost, and because AFC keeps shrinking, ATC and AVC squeeze closer together as output grows. Nailing AFC is how you make sense of the whole short-run cost diagram the exam loves to test.
Keep studying AP Microeconomics Unit 3
Average Total Cost (Unit 3)
ATC = AVC + AFC, which means the distance between the ATC and AVC curves is exactly AFC. As AFC falls, that gap narrows, so ATC and AVC drift toward each other at high output.
Total Fixed Cost (Unit 3)
AFC is just Total Fixed Cost spread per unit. TFC is a flat horizontal line that never changes with output, but dividing it by a rising quantity gives you the constantly falling AFC curve.
Average Variable Cost (Unit 3)
AVC handles the costs that change with output, while AFC handles the ones that don't. Add them and you get ATC. Knowing which costs are fixed versus variable is the whole game when filling out a cost table.
Long Run (Unit 3)
In the long run all inputs are adjustable, so every cost becomes variable (EK PRD-1.A.9). That means AFC exists only in the short run and vanishes once a firm can change its plant size and other fixed inputs.
AFC shows up mostly inside cost-table and cost-curve problems rather than as a standalone question. On the 2024 FRQ Q2, a short-run production table for a cat food firm asked you to work through productivity and cost measures, the exact skill set in AP Micro 3.3.C where you calculate short-run costs from data. Expect to compute AFC by dividing total fixed cost by quantity, and to recognize on a graph that AFC is the falling gap between ATC and AVC. MCQs often test whether you know AFC always decreases as output rises and that fixed costs disappear from the analysis in the long run when all factors of production become variable.
AFC comes from costs that don't change with output (so it always falls), while AVC comes from costs that do change with output (so it's U-shaped, falling then rising). The two together add up to ATC, and the distance between ATC and AVC on a graph is your AFC.
Average Fixed Cost equals Total Fixed Cost divided by quantity of output.
AFC always falls as output rises because the same fixed cost is spread over more units.
The vertical gap between the ATC and AVC curves is exactly equal to AFC.
AFC exists only in the short run; in the long run all costs become variable and AFC drops out.
Because AFC keeps shrinking, the ATC and AVC curves move closer together at higher output.
It's a firm's total fixed cost divided by the quantity it produces, telling you how much fixed cost each unit carries. It's a short-run concept covered in Unit 3, Topic 3.3.
Because total fixed cost stays constant no matter how much you produce, dividing that fixed amount by a larger and larger quantity gives a smaller per-unit figure every time. So the AFC curve slopes downward forever and never rises.
AFC comes from costs that don't change with output, so it continuously falls, while AVC comes from costs that change with output, so it's U-shaped. Add them together and you get Average Total Cost.
No. In the long run firms can adjust all their inputs (EK PRD-1.A.9), so every cost becomes variable and there are no fixed costs to average. AFC is purely a short-run idea.
AFC is the vertical distance between the ATC curve and the AVC curve at any given quantity. Since that gap shrinks as output grows, the two curves get closer together farther right on the graph.