Average Fixed Cost Calculator (AFC, AVC & ATC per unit)

Understanding the average fixed cost calculator — concept and principle

This calculator finds average fixed cost (AFC), the fixed cost carried by each unit produced, together with average variable cost (AVC), average total cost (ATC) and total cost. It can also show how AFC changes at a second output level. Economics students and small producers use it to understand unit costs and why producing more lowers the cost per unit.

Fixed cost spread over more units — with the default inputs: −33.3%.

How it is calculated

AFC = total fixed cost ÷ output (TFC ÷ Q)
AVC = total variable cost ÷ output (TVC ÷ Q)
ATC = total cost ÷ output = AFC + AVC, where TC = TFC + TVC
Fixed-cost share = TFC ÷ TC × 100
AFC at another output Q2 = TFC ÷ Q2; change = (Q ÷ Q2 − 1) × 100

Costs are for the same period as the output, in your chosen currency.

The principle

In the short run, fixed costs such as rent, salaried staff and depreciation do not change with output. Spreading the same total over more units makes each unit's share smaller, so AFC falls continuously as output rises. Because AFC × Q always equals TFC, the AFC curve is a rectangular hyperbola: it falls steeply at low output and flattens out, but never reaches zero. Variable costs behave differently: they rise with output, and AVC can fall and later rise. ATC combines the two, which is why it is usually U-shaped in textbook diagrams.

Worked example

Defaults: fixed costs 12,000; 3,000 units; variable costs 18,000; comparison output 4,500 units.

AFC = 12,000 ÷ 3,000 = $4.00.
AVC = 18,000 ÷ 3,000 = $6.00.
Total cost = 12,000 + 18,000 = $30,000; ATC = 30,000 ÷ 3,000 = $10.00.
Fixed-cost share = 12,000 ÷ 30,000 × 100 = 40%.
AFC at 4,500 units = 12,000 ÷ 4,500 = $2.67; change = (3,000 ÷ 4,500 − 1) × 100 = −33.3%.

Each point is the calculator re-run with only “Units produced in the period” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Units produced in the period	Average fixed cost per unit
750	$16.00
1,500	$8.00
2,250	$5.33
3,000	$4.00
3,750	$3.20
4,500	$2.67
6,000	$2.00

How to read the result

A high fixed-cost share means unit cost is very sensitive to volume: selling more brings large savings per unit, and a drop in sales hurts quickly. A low share means most costs move with output, so volume matters less. Use ATC as the minimum average price needed to cover all costs at that volume. At the comparison output only AFC is recalculated; AVC may also change in reality.

Common mistakes

Putting materials or piece-rate pay into fixed costs.
Assuming fixed costs stay fixed forever; a new machine or larger premises raises them in steps.
Using AFC alone to set prices; the price must cover AVC as well.
Mixing a monthly cost with a yearly output.

Keep in mind: The split between fixed and variable cost is a simplification valid over a limited range of output. Results are estimates, not accounting or financial advice.

Frequently asked questions

Does average fixed cost ever increase?

Not while total fixed cost is unchanged. It rises only if output falls or fixed costs themselves increase.

What is the difference between AFC and ATC?

AFC is fixed cost per unit only; ATC adds variable cost per unit and is the full cost per unit.

Why does AFC never reach zero?

Dividing a positive fixed cost by any finite output always leaves a positive number.

Sources: OpenStax, Principles of Microeconomics, section 7.2 "The Structure of Costs in the Short Run" · NCERT / CIET (India), Economics Class XII e-content module "Concept of Cost"

Checked 9 Nov 2026. Definitions TC = TFC + TVC, AFC = TFC/Q, AVC = TVC/Q, ATC = TC/Q = AFC + AVC and the rectangular-hyperbola shape of AFC: NCERT / CIET (India), Economics Class XII e-content module “Concept of Cost – Part 4”; ATC = TC ÷ Q also in OpenStax “Principles of Microeconomics”, section 7.2 “The Structure of Costs in the Short Run”.

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