BUSS1030 Chap.2 Cost Behaviour and CVP
Cost Behaviour and CVP
Cost-volume-profit analysis converts a business plan into relationships among selling price, variable cost, fixed cost, volume and profit. This chapter builds contribution margin, break-even, target-profit volume and margin of safety, then uses sensitivity analysis to compare alternative plans. Every result is checked against the revenue and total-cost relationship before it becomes a recommendation.
The method begins by classifying costs within a stated relevant range. Fixed cost supplies the platform that must be covered, while contribution margin measures how much each sale provides after its variable cost. Break-even is therefore a relationship rather than a mysterious target: total contribution equals fixed cost and profit is zero. Target-profit analysis adds the required return before dividing by contribution.
Margin of safety then compares forecast demand with the break-even boundary and provides a simple view of exposure to a sales decline. The chapter emphasises units throughout because a contribution per unit, total dollars and a percentage ratio answer different questions. It also tests direction before accepting arithmetic.
Higher fixed cost or variable cost should raise break-even, while a higher selling price normally lowers it if demand and other assumptions remain unchanged. Alternative plans can trade a larger fixed commitment for a stronger contribution margin, producing a crossover volume at which the preferred choice changes.
Multi-product situations add a sales-mix assumption and require a composite bundle rather than one product's contribution alone. These tools do not predict demand or guarantee capacity. They support a recommendation only when price, cost behaviour, mix, capacity and the likely response of customers are made explicit and sensitivity analysis shows how a plausible change affects the choice.
What this chapter covers
- 01
Fixed and variable costs
- 02
Contribution margin
- 03
Break-even units
- 04
Target-profit volume
- 05
Margin of safety
- 06
Sensitivity and crossover
Worked example · free
Break-even and target profit for a meal-box stall
- +1Contribution per box is $18 minus $10 = $8.
- +2Break-even units are $2,400 divided by $8 = 300.
- +2Target-profit units are ($2,400 + $1,200) divided by $8 = 450.
- +1At 300 boxes, revenue and total cost both equal $5,400.
Key terms
- Variable cost
- A cost whose total changes with activity while the per-unit amount is assumed stable within the relevant range.
- Fixed cost
- A cost whose total is assumed unchanged across the relevant activity range for the planning period.
- Contribution margin
- Selling price minus variable cost, available to cover fixed cost and then profit.
- Margin of safety
- The amount by which expected or actual sales exceed break-even sales.
Cost Behaviour and CVP FAQ
Why is contribution margin calculated first?
Contribution margin is the amount each unit provides toward fixed cost and profit. Break-even, target-profit volume and expected profit all depend on it, so a wrong contribution figure contaminates every later result.
When should a break-even answer be rounded up?
When the result is a number of indivisible units, round upward because the lower whole number does not fully cover fixed cost. Keep decimal precision when the activity can be measured continuously or when the question asks for sales dollars.
What limits a CVP recommendation?
The basic model assumes stable price, stable variable cost per unit, unchanged fixed cost within a relevant range and a known sales mix. Capacity, demand, discounts and step costs can reverse the conclusion.
Exam move
Draw the revenue and total-cost lines once, then link every formula to the picture. Rework each example after changing one lever and predict the direction before calculating. Always verify break-even by proving revenue equals total cost, and end target-profit questions by stating whether expected volume reaches the target. Create a four-column drill headed price, variable cost, fixed cost and volume.
Change one input at a time, predict what happens to contribution and break-even, then calculate. The prediction should come before the arithmetic so a reversed result becomes visible. Practise both unit and sales-dollar versions, keeping units on every line. For target profit, write fixed cost plus target profit in the numerator rather than trying to adjust break-even after the calculation.
Add a margin-of-safety sentence to each solution: expected sales exceed break-even by a stated number of units or dollars. Once single-plan questions are fluent, compare two alternatives with different fixed and variable structures. Calculate profit at a low and high volume, then solve the crossover and explain which plan wins on each side. Review assumptions separately from formulas.
Ask whether price, unit variable cost, fixed cost, capacity and sales mix are reasonably stable. In timed practice, use a fixed sequence: contribution, break-even, target volume, expected profit, margin of safety, decision. Check break-even by recomputing revenue and total cost independently. A correct division with a failed equality check is not finished.
End by naming the commercial lever management could change and the demand or capacity assumption that could defeat the recommendation.
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