Foundations
Fixed versus Variable Costs
The distinction between costs that remain in place and costs that move with activity.
Mental model
Fixed costs stay in place while variable costs move with activity, changing how volume reaches profit.
A variable cost follows each unit of demand. A fixed cost is paid even when the next unit never arrives.
The distinction makes break-even analysis possible: contribution from activity must first cover the fixed base.
Explore the mechanism
How does the cost base respond when activity rises, falls, or stops?
Variable cost follows activity. Fixed cost does not. Contribution must first cover the fixed base before profit becomes positive.
At 75 units, variable cost is 300 while fixed cost remains 300. Profit is 150.
What to notice
A cost can be fixed over one horizon and variable over another. Time and reversibility matter.
Stress tests become more realistic when they model which costs can actually be removed after demand changes.
Where it appears
- break-even analysis
- capacity investment decisions
- stress-testing capital-intensive businesses
Where the intuition breaks
What this view leaves out
- Costs are rarely perfectly fixed or variable across all horizons; contracts, step costs, and renegotiation make the classification time-dependent.
Where this concept sits
Follow the strongest prerequisites, applications, extensions, and contrasts.
Connections for Fixed versus Variable Costs
Operating leverage exists because the cost base contains costs that do not move one-for-one with activity.
SupportsCapacity UtilizationSeparating fixed capacity costs from activity-dependent costs explains why unit economics change as utilization rises or falls.
Operating leverage exists because the cost base contains costs that do not move one-for-one with activity.
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