Management Accounting · Applications of Marginal Costing in Short Term Decision Making

Marginal Costing Basics and Contribution Analysis

Updated 10 October 2026 · Fact-checked

Marginal costing charges only variable costs to products and treats fixed costs as a period cost written off against total contribution. Contribution = Sales − Variable cost. P/V ratio = Contribution ÷ Sales. To solve a question, split costs into variable and fixed, find contribution, then profit = contribution − fixed cost.

Understand Marginal Costing Basics and Contribution Analysis

Marginal cost is the extra cost of making one more unit. In exams it is the variable cost per unit: direct material, direct labour, direct expenses and variable overhead. It changes with output.

Fixed costs stay the same in total over a relevant range of output and a given period, such as factory rent or supervisor salary. Per unit they fall as output rises. Marginal costing does not spread them over units. It charges the whole amount to the period's profit statement.

Contribution is what each unit of sales leaves after covering its variable cost. It first pays for fixed costs. Once fixed costs are covered, the rest is profit. So Profit = Contribution − Fixed cost. This is why you can see at once how profit moves when sales change.

The P/V ratio (profit volume ratio, also called contribution to sales ratio) shows contribution as a share of sales. A higher ratio means each rupee of sales adds more towards fixed costs and profit. If fixed costs do not change, a change in sales changes profit by the change in sales × P/V ratio.

For short-term decisions you use relevant cost: a future cost that differs between the alternatives. Differential cost is the difference in cost between two alternatives. Sunk (past) costs and committed costs that do not change are ignored. Fixed costs are relevant only if the decision changes them. Marginal costing differs from absorption costing in how it treats fixed overhead and stock. Marginal costing values stock at variable cost only. Absorption costing includes a share of fixed production overhead in stock.

Key rules to remember

Contribution: Contribution = Sales − Variable cost; Also Contribution = Fixed cost + Profit. Per unit: selling price − variable cost per unit.
Profit: Profit = Contribution − Fixed cost; If contribution is less than fixed cost, the result is a loss.
P/V ratio: P/V ratio = Contribution ÷ Sales × 100; Also = Change in profit ÷ Change in sales, when fixed cost is unchanged.
Variable cost ratio: Variable cost ratio = Variable cost ÷ Sales = 1 − P/V ratio; Use it to move quickly between cost and contribution.
Break-even sales: Break-even sales = Fixed cost ÷ P/V ratio; Break-even units = Fixed cost ÷ Contribution per unit.
Margin of safety: Margin of safety = Actual sales − Break-even sales = Profit ÷ P/V ratio; Gives the sales cushion before a loss starts.
Marginal costing stock value: Stock valued at variable cost only; Absorption costing adds fixed production overhead to stock value.
Relevant cost rule: Relevant cost = future, avoidable cost that differs between alternatives; Ignore sunk and unavoidable costs.

How to solve Marginal Costing Basics and Contribution Analysis questions

Use this order for any marginal costing question. It keeps the layout clean and earns step marks.

1Read what is asked: contribution, P/V ratio, profit at a new volume, or a decision.
2Classify every cost as variable or fixed. Treat semi-variable costs by splitting them if data allows.
3Work out per-unit selling price and variable cost, then contribution per unit.
4Calculate total contribution for the given volume and the P/V ratio.
5Deduct fixed costs from total contribution to get profit. Show it as a marginal cost statement.
6For decisions, list only relevant (future, differing) costs and revenues and compare the contribution of each alternative.
7Check that fixed costs have not been wrongly spread over units or wrongly included.
8State the conclusion in a sentence, and mention any non-financial factor if the question hints at one.

Quickest way: Contribution-first shortcut

When to use it: Use in MCQs and in the first lines of a numerical when sales, variable cost and fixed cost are given.

Find contribution per unit or total contribution straight away.
Get the P/V ratio = contribution ÷ sales.
For a change in sales, profit change = sales change × P/V ratio (fixed cost constant).
Break-even sales = fixed cost ÷ P/V ratio.
Verify with one quick calculation: contribution − fixed cost = profit.

Common mistakes in Marginal Costing Basics and Contribution Analysis

Treating fixed cost per unit as variable and multiplying it by new volume
The question gives a per-unit figure for all costs, so it looks variable.
Fix: Convert fixed cost back to total (per unit × original units) and keep it constant for the new volume within the relevant range.
Deducting fixed cost when calculating contribution
Students confuse contribution with profit.
Fix: Contribution = Sales − Variable cost only. Fixed cost comes off afterwards.
Including sunk costs or unchanged allocated overheads in a decision
Students take every cost in the problem as relevant.
Fix: Ask: will this cost change if I choose this option? If not, leave it out.
Valuing closing stock at full cost in marginal costing
Habit from absorption costing.
Fix: Under marginal costing value stock at variable production cost only. Fixed cost goes to the period.
Calculating P/V ratio on units or costs instead of sales
The denominator is mixed up.
Fix: Always divide contribution by sales value, and write it as a percentage.

Worked examples

Example 1

A company sells 20,000 units at ₹50 per unit. Variable cost is ₹30 per unit. Fixed cost is ₹2,40,000. Find (a) contribution per unit, (b) P/V ratio, (c) profit, (d) profit if sales rise by ₹2,00,000 with fixed cost unchanged.

Show the solution

Contribution per unit = 50 − 30 = ₹20.
Sales = 20,000 × 50 = ₹10,00,000. Total contribution = 20,000 × 20 = ₹4,00,000.
P/V ratio = 4,00,000 ÷ 10,00,000 = 40%.
Profit = 4,00,000 − 2,40,000 = ₹1,60,000.
Extra contribution = 2,00,000 × 40% = ₹80,000. Fixed cost unchanged, so new profit = 1,60,000 + 80,000 = ₹2,40,000.

Answer: Contribution ₹20 per unit; P/V ratio 40%; profit ₹1,60,000; new profit ₹2,40,000.

Example 2

Aarav Ltd makes a product with a selling price of ₹80 per unit, variable cost of ₹48 per unit and fixed cost of ₹3,20,000. A customer offers to buy 5,000 extra units at ₹60 per unit. Existing capacity is idle and fixed cost will not change. Should the order be accepted? Find the effect on profit.

Show the solution

Relevant revenue per unit = ₹60. Relevant cost per unit = variable cost ₹48.
Contribution per unit on the order = 60 − 48 = ₹12.
Total extra contribution = 5,000 × 12 = ₹60,000.
Fixed cost is unchanged and so is irrelevant. The full cost per unit (including fixed cost) is not used.
Since contribution is positive and there is no effect on regular sales, accepting adds to profit.

Answer: Accept the order. Profit rises by ₹60,000, provided regular sales and prices are not affected.

Exam tips

In an MCQ, compute contribution and P/V ratio first. Most options follow from them.
Present a marginal cost statement with headings: Sales, Variable cost, Contribution, Fixed cost, Profit. It earns step marks even if the final figure slips.
In decision questions, write a short line stating which costs you ignored and why (sunk, unavoidable, committed).
When asked for the difference between marginal and absorption costing, cover cost treatment, stock valuation and profit effect in separate points.
Write the conclusion in words. ICMAI expects a recommendation, not just a number.

Practice questions from Applications of Marginal Costing in Short Term Decision Making

Marginal Costing Basics and Contribution Analysis in other exams

The same ground in other exams, if you are preparing for more than one or want another angle on it.

Marginal Costing Basics and Contribution Analysis: frequently asked questions

What is the difference between marginal cost and contribution?

Marginal cost is the variable cost of one more unit. Contribution is selling price less that marginal cost. Contribution is what is left to cover fixed costs and give profit.

How do you calculate the P/V ratio?

Divide contribution by sales and multiply by 100. You can also divide the change in profit by the change in sales, if fixed cost stays the same.

What is the difference between marginal costing and absorption costing?

Marginal costing treats fixed costs as period costs and values stock at variable cost. Absorption costing spreads fixed production overhead over units, so stock carries part of it. Profit can differ when opening and closing stock differ.

What is relevant cost in decision making?

It is a future cost that will change depending on the choice made. Sunk costs and costs that stay the same under every option are not relevant.