IB Business Management HLTopic 6 — The Business Management ToolkitPapers 1, 2 & 3HL only~11 min read
Using Contribution Analysis
Contribution answers one question: when you sell one more unit, how much is left over after paying that unit’s own costs? Whatever is left goes towards the bills the business has to pay whether it sells anything or not. Get this idea and make-or-buy, break-even and product decisions all become easy.
📘 What you need to know
Contribution per unit = selling price − variable cost per unit.
Total contribution = contribution per unit × units sold.
Contribution pays the fixed costs first. Anything after that is profit.
Contribution costing charges only direct costs to a product; fixed costs are treated as a lump paid by the whole business.
Absorption costing shares the fixed costs out across products, so each one carries its own slice.
Make or buy: compare the cost to make with the cost to buy, and check whether the volume is high enough to cover the fixed costs of making.
Where the money goes
Notice the order. Contribution does not become profit until every fixed cost has been covered, which is why break-even is just fixed costs divided by contribution.
The three formulas
Contribution per unit = price − variable cost per unit
Total contribution = contribution per unit × units sold
Break-even units = fixed costs ÷ contribution per unit
Worked examples
WORKED EXAMPLE
Bright Batch sells its signature loaf for $9.50. Variable costs are $3.70 per loaf and fixed costs are $8,700 a month. Calculate the contribution per loaf, the break-even output, and the profit if it sells 2,400 loaves. [4 marks]
Step 1: contribution per unit$9.50 − $3.70 = $5.80Step 2: break-even output$8,700 ÷ $5.80 = 1,500 loavesStep 3: total contribution at 2,400 loaves$5.80 × 2,400 = $13,920Step 4: profit$13,920 − $8,700 = $5,220$5.80 per loaf, break-even 1,500, profit $5,220every loaf after number 1,500 adds a clean $5.80 of profit
Make or buy
Should a business produce something itself or order it from a supplier? Making it in-house is cheaper per unit but brings fixed costs. Buying it in costs more per unit but avoids those fixed costs. The answer depends on how many you expect to sell.
The break-even volume for making
fixed costs ÷ (cost to buy − cost to make)
WORKED EXAMPLE
Loop Cycles can make its own brake pads for $4.20 a set or buy them for $5.00. Making them means $9,600 a year of extra fixed costs. Loop expects to use 7,000 sets a year. Advise Loop. [4 marks]
Step 1: saving per set if Loop makes them$5.00 − $4.20 = $0.80Step 2: how many sets to cover the fixed costs$9,600 ÷ $0.80 = 12,000 setsStep 3: compare with expected volumeLoop expects only 7,000 sets, which is well below the 12,000 needed [1].Step 4: adviseLoop should buy the pads from the supplier. Making them would leave roughly $4,000 of fixed costs uncovered [1].Buy in: volume is too low to justify makingthe saving per unit is never the whole answer — volume decides it
Numbers are not the whole decision. Make or buy also depends on spare capacity, whether the business has the skills, how urgently the parts are needed, how reliable the supplier is, and whether exchange rates or import rules could push the buying price up.
Contribution costing versus absorption costing
Point
Contribution costing
Absorption costing
What is charged to a product
Direct costs only
Direct costs plus a share of the fixed costs
How fixed costs are treated
Paid by the business as a whole
Split across products or departments
Best for
Comparing which product earns most per sale
Setting prices that cover every cost
Main risk
Can look profitable while fixed costs go unpaid
The split is a judgement, so a product can look worse than it is
Typical split method
Not applicable
Equal shares, floor space, sales volume or number of staff
A product with positive contribution is worth keeping even if absorption costing shows it making a loss. It is still helping to pay the rent. Drop it and the rent does not go away — it just gets shared among fewer products.
How useful is contribution analysis?
Strength
Weakness
Simple to calculate and quick to compare products
Assumes variable cost per unit stays the same at every level of output
Shows which product earns most from each sale
Ignores qualitative factors such as skills, quality and supplier reliability
Underpins break-even and make-or-buy decisions
Splitting costs into fixed and variable is not always clear-cut
Stops a business dropping a product that is helping pay the rent
Says nothing about whether demand will actually be there
Works with limited data, which suits smaller firms
Absorption methods can make the same product look profitable or not
💡 Exam tips
Label everything: “contribution per unit”, “total contribution”, “profit”. They are three different numbers.
Show the formula, then the substitution, then the answer. Method marks are generous.
Keep the units. Break-even answers are in units sold, not dollars.
For make-or-buy, always finish by comparing the break-even volume with expected demand.
Add one qualitative factor at the end. It converts a calculation into an argument.
If asked to drop a product, check the contribution first. Positive contribution usually means keep it.
⚠ Common mix-ups
Calling contribution “profit”. It is profit only after fixed costs are covered.
Subtracting fixed costs per unit when working out contribution. Only variable costs come off.
Dividing by the wrong number in break-even. It is fixed costs over contribution per unit.
Ignoring fixed costs in make-or-buy and choosing the cheaper unit cost automatically.
Dropping a product because absorption costing shows a loss while its contribution is positive.
Assuming variable cost per unit never changes. Bulk discounts and overtime both break that.
Up next: Using Critical Path Analysis — back to projects, and the tool that works out the shortest possible time and which tasks you absolutely cannot afford to delay.
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