Fixed cost per unit falls as output rises while total fixed cost remains unchanged within the relevant range. Total spending can stay unchanged. This distinction matters when comparing unit costs or explaining why a busy month looks cheaper per unit.
Fixed cost per unit: work with total costs first
Assume a workshop has fixed costs of PKR 120,000 per month and variable costs of PKR 30 per unit. It can produce either 4,000 or 6,000 units within existing capacity. There are no other costs in this simplified example.
| Measure | 4,000 units | 6,000 units |
|---|---|---|
| Total fixed cost | PKR 120,000 | PKR 120,000 |
| Total variable cost | PKR 120,000 | PKR 180,000 |
| Total cost | PKR 240,000 | PKR 300,000 |
| Fixed cost per unit | PKR 30 | PKR 20 |
| Variable cost per unit | PKR 30 | PKR 30 |
| Total cost per unit | PKR 60 | PKR 50 |
At 6,000 units, average cost is lower, but total cost is higher. The workshop has produced more units and incurred more variable cost. It has not saved PKR 10 on every existing unit through a reduction in its rent or other fixed spending.
Explain the pattern in words
Total variable cost rises with output under the constant-rate assumption. Variable cost per unit stays at PKR 30. Total fixed cost stays at PKR 120,000, while fixed cost per unit falls from PKR 30 to PKR 20.
A strong answer names the total and the per-unit figure. Writing only “fixed costs decrease” would be misleading because it does not say which measure you mean.
Check the relevant range
Suppose output above 6,500 units needs a second workshop with extra monthly rent. The original fixed-cost assumption would no longer be suitable. Costs might rise in steps rather than remaining constant indefinitely.
Other assumptions can change too. Overtime, bulk discounts, waste or a new supplier may alter the variable cost per unit. Use the information in the question rather than extending a simple model beyond its stated range.
A short practice task
With fixed costs of PKR 90,000 and variable cost of PKR 15 per unit, calculate total cost per unit at 3,000 units. Then calculate it at 5,000 units, assuming both outputs are within the relevant range.
Answer: at 3,000 units, fixed cost per unit is PKR 30 and total cost per unit is PKR 45. At 5,000 units, the figures are PKR 18 and PKR 33. Total fixed cost is unchanged in both cases.
For further foundations practice, visit the MA1 course. Confirm the scope of your revision using the current MA1 syllabus guide.
Use a formula that keeps totals separate
With total fixed cost F, variable cost per unit v and output Q, total cost is F plus v multiplied by Q. Average cost per unit is F divided by Q plus v. The formulas describe the same model from two viewpoints. At low output, each unit carries a larger share of the fixed amount. As output rises, that share falls while the variable amount per unit remains unchanged under the model’s assumptions.
Using the original workshop, total cost at 5,000 units is PKR 120,000 plus PKR 30 multiplied by 5,000, or PKR 270,000. Dividing by 5,000 gives PKR 54 per unit. Check it another way: fixed cost per unit is PKR 24 and variable cost per unit is PKR 30. Both methods give the same answer. This cross-check can reveal an incorrect denominator or a forgotten variable component.
What happens when output falls?
If output falls to 2,000 units while the fixed commitment remains PKR 120,000, fixed cost per unit becomes PKR 60. Total variable cost is PKR 60,000 and total cost is PKR 180,000. Average cost is PKR 90. Spending is lower than at 4,000 units because fewer variable inputs are used, but each unit carries more of the unchanged fixed amount.
A rise in average cost does not necessarily mean the workshop became less efficient at using materials. It may reflect unused capacity. To distinguish those explanations, compare output, variable usage per unit and fixed commitments. An average combines several effects and should not be treated as a direct measure of a single operational improvement or deterioration.
Calculate a capacity step explicitly
Assume the workshop can produce up to 6,500 units with fixed costs of PKR 120,000. Producing more requires an additional facility costing PKR 60,000 per month. At 7,000 units, fixed costs become PKR 180,000, not PKR 120,000. With the same PKR 30 variable rate, total cost is PKR 390,000 and average cost is approximately PKR 55.71.
This average is higher than the PKR 50 at 6,000 units despite the greater output. The new capacity step has increased the numerator. Once the additional facility is in place, further output within its range may spread PKR 180,000 over more units. The pattern can therefore fall, jump and fall again; it is not necessarily a smooth decline across all possible volumes.
Do not confuse average cost with extra cost
At 4,000 units, the original average is PKR 60. If producing one additional unit uses PKR 30 of variable inputs and no extra fixed commitment, the incremental cost in this simplified case is PKR 30. The average of PKR 60 includes fixed costs already committed for the period. Multiplying it by the extra unit would not identify the change in total cost correctly.
This does not mean a business should always charge only variable cost. Pricing must consider capacity, long-term cost recovery and the wider commercial situation. It means that average reporting cost and the additional cost of a particular decision answer different questions. Read which measure the exam question requests before selecting a number.
Separate production volume from sales volume
The workshop table measures cost per unit produced. If a question asks for profit or break-even, sales volume also matters. Producing more units does not automatically generate more revenue if those units remain unsold. Inventory accounting can affect when production costs enter profit, and a simple unit-cost table is not enough to infer that the business earned more.
For introductory questions, follow the stated assumptions about production and sales. If both are equal, say so. If they differ, do not quietly use one as the other. A clear label such as cost per unit produced protects the calculation from being interpreted as cost per unit sold or profit per unit.
Read cost graphs by their axes
A graph of total fixed cost against output is horizontal within the relevant range. A graph of fixed cost per unit slopes downward as output increases. A graph of total variable cost rises from the origin when the rate is constant and there is no fixed component. Variable cost per unit is horizontal under the same assumption. Different shapes can describe the same underlying cost.
Always read whether the vertical axis shows a total or a per-unit amount. Many wrong answers come from identifying a familiar shape without checking the axis label. Add the reporting period and output range to your explanation so the graph’s assumptions are visible.
A final reasoning check
Before submitting an answer, ask whether the fixed total stayed the same, whether the variable rate stayed the same and whether output remained inside the capacity range. Recalculate total cost before dividing. Then explain the result using both total and average figures. This method helps you avoid describing a falling average as a cash saving that never occurred.
Frequently asked questions
Does a lower fixed cost per unit mean total fixed costs fell?
No. The same total fixed cost can be spread across more units, reducing its average per unit without reducing spending.
Will fixed costs stay unchanged at every output level?
Not necessarily. Fixed-cost assumptions apply within a relevant activity range and time period. Extra capacity can introduce additional fixed costs.