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Fundamentals of Financial and Cost Accounting · Application of Cost Accounting for Business Decisions

Marginal Costing Basics and Contribution Explained

Updated 10 October 2026 · Fact-checked

Marginal costing charges only variable costs to products and treats fixed costs as period costs written off against total contribution. Contribution = Sales − Variable cost. Profit = Contribution − Fixed cost. To solve a question, find variable cost per unit, compute contribution, then subtract fixed cost to get profit.

Understand Marginal Costing Basics and Contribution

Marginal cost is the extra cost of producing one more unit. In exam problems it is usually the same as the variable cost per unit: direct material, direct labour, direct expenses and variable overheads.

Marginal costing is a technique where only variable costs are charged to units produced. Fixed costs, such as rent and salaries of the factory manager, do not go into product cost. They are treated as a cost of the period and written off in full against the contribution earned.

Contribution is sales minus variable cost. Think of it as the amount each sale 'contributes' first towards covering fixed cost, and then towards profit. If contribution is more than fixed cost, you make a profit. If it is less, you make a loss. If it equals fixed cost, you break even.

In marginal costing, stock is valued at variable cost only. In absorption costing (full costing), stock is valued at variable cost plus a share of fixed production overhead. This difference in stock valuation is why the two methods can show different profits when opening and closing stocks differ.

Key features of marginal costing: costs are split into fixed and variable, fixed costs are period costs, stock is valued at marginal cost, and profit is judged through contribution. It is useful for pricing, make-or-buy and product-mix decisions.

Key formulas to remember

Marginal cost
Marginal cost = Direct material + Direct labour + Direct expenses + Variable overheads
Variable overheads include variable factory, administration and selling overheads when asked for total variable cost.
Contribution
Contribution = Sales − Variable cost
Variable cost here includes variable selling cost on units sold.
Marginal cost equation
Sales − Variable cost = Contribution; Contribution − Fixed cost = Profit
Equivalent form: Sales − Variable cost = Fixed cost + Profit.
Contribution per unit
Contribution per unit = Selling price per unit − Variable cost per unit
Total contribution = Contribution per unit × Units sold.
P/V ratio
P/V ratio = Contribution ÷ Sales × 100
Also called contribution to sales ratio. Contribution = Sales × P/V ratio.
Profit difference between the two methods
Absorption profit − Marginal profit = Fixed overhead in closing stock − Fixed overhead in opening stock
Use the fixed overhead rate per unit × change in stock units, when the rate is the same in both years.

How to solve Marginal Costing Basics and Contribution questions

Use this order for any marginal costing question, whether it asks for contribution, profit or a comparison of the two costing methods.

  1. 1Read what is asked: contribution, profit, marginal cost statement, or the profit difference between methods.
  2. 2List all costs and tag each as variable or fixed. Check carefully for variable selling and administration costs.
  3. 3Find variable cost per unit and selling price per unit.
  4. 4Compute contribution per unit, then total contribution on units sold (not units produced).
  5. 5Subtract total fixed cost from total contribution to get profit or loss.
  6. 6If comparing with absorption costing, value stock at variable cost for marginal costing and at variable plus fixed production cost for absorption costing.
  7. 7Check using the equation: Sales − Variable cost − Fixed cost = Profit. Confirm the units used are the right ones.

Quickest way: Contribution first, fixed cost last

When to use it: Use for most MCQs where sales, variable cost and fixed cost are given and you need profit, contribution or fixed cost.

  1. Write the one-line equation: S − V = F + P.
  2. Fill in the three values you know and solve for the missing one.
  3. For per-unit data, find contribution per unit first and multiply by units sold.
  4. For absorption versus marginal profit gaps, ignore everything else: gap = fixed overhead per unit × change in stock units.
  5. Eliminate options that use units produced instead of units sold, or that forget fixed cost.

Common mistakes in Marginal Costing Basics and Contribution

  • Treating fixed cost as part of product cost under marginal costing.

    Students are used to absorption costing, where overheads are added to cost.

    Fix: Under marginal costing, only variable costs go into product cost and stock value. Fixed cost is deducted in full from contribution.

  • Calculating contribution on units produced instead of units sold.

    Production and sales figures are both given, and students pick the wrong one.

    Fix: Contribution and sales always relate to units sold. Production matters only for stock valuation and absorption costing.

  • Leaving out variable selling and distribution costs from variable cost.

    Students think only production costs are variable.

    Fix: Include every cost that changes with sales volume, such as sales commission per unit, when computing contribution.

  • Confusing contribution with profit.

    Both are surplus figures and the names sound alike.

    Fix: Contribution is before fixed cost. Profit is after fixed cost. Profit = Contribution − Fixed cost.

  • Valuing closing stock at full cost under marginal costing.

    Habit from financial accounting, where stock includes production overheads.

    Fix: Under marginal costing, value stock at variable cost per unit only.

  • Getting the sign wrong when explaining profit difference.

    Students forget which method carries fixed cost into stock.

    Fix: If stock rises, absorption costing shows higher profit, since more fixed cost is carried forward. If stock falls, marginal costing shows higher profit.

Worked examples

Example 1

A company sells 10,000 units at ₹50 per unit. Variable cost is ₹30 per unit and fixed cost is ₹1,50,000. Find the contribution, P/V ratio and profit.

Show the solution
  1. Contribution per unit = 50 − 30 = ₹20.
  2. Total contribution = 20 × 10,000 = ₹2,00,000.
  3. Sales = 50 × 10,000 = ₹5,00,000.
  4. P/V ratio = 2,00,000 ÷ 5,00,000 × 100 = 40%.
  5. Profit = Contribution − Fixed cost = 2,00,000 − 1,50,000 = ₹50,000.

Answer: Contribution ₹2,00,000; P/V ratio 40%; profit ₹50,000.

Example 2

A firm produced 5,000 units and sold 4,000 units. There was no opening stock. Selling price is ₹100 per unit, variable cost is ₹60 per unit and fixed production overhead is ₹1,00,000 (absorbed on units produced). There are no other costs. Find profit under marginal costing and absorption costing, and the difference.

Show the solution
  1. Marginal costing: contribution = (100 − 60) × 4,000 = ₹1,60,000.
  2. Profit = 1,60,000 − 1,00,000 = ₹60,000.
  3. Fixed overhead per unit = 1,00,000 ÷ 5,000 = ₹20.
  4. Closing stock = 5,000 − 4,000 = 1,000 units.
  5. Absorption costing: cost per unit = 60 + 20 = ₹80. Profit = (100 − 80) × 4,000 = ₹80,000.
  6. Difference = 80,000 − 60,000 = ₹20,000.
  7. Check: fixed overhead in closing stock = 1,000 × 20 = ₹20,000, which matches.

Answer: Marginal costing profit ₹60,000; absorption costing profit ₹80,000; difference ₹20,000, because closing stock carries ₹20,000 of fixed overhead.

Exam tips

  • Most questions are numeric and fast. Write S − V = F + P first, then fill in the numbers.
  • Always check whether the question gives units produced and units sold separately. Use sold units for contribution.
  • For profit differences between the two methods, calculate only the fixed overhead in stock change. It saves time.
  • Watch for the words 'marginal cost' and 'variable cost' used interchangeably in options, and read each option fully.
  • Since there is no negative marking, attempt every question. Eliminate options that ignore fixed cost or use the wrong units.

Practice questions from Application of Cost Accounting for Business Decisions

Marginal Costing Basics and Contribution 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: frequently asked questions

What is the marginal cost equation?

It is Sales − Variable cost = Contribution, and Contribution − Fixed cost = Profit. You can also write it as Sales − Variable cost = Fixed cost + Profit. Use it to find any one missing value.

What is the difference between marginal costing and absorption costing?

Marginal costing charges only variable costs to products and writes off fixed cost in the period. Absorption costing charges both variable and fixed production costs to products. Stock is valued differently, so profits differ when stock levels change.

Is contribution the same as profit?

No. Contribution is sales minus variable cost, before fixed cost. Profit is what remains after fixed cost is also deducted. Contribution equals profit only when fixed cost is zero.

When do marginal costing and absorption costing give the same profit?

They give the same profit when opening stock equals closing stock in units, assuming the fixed overhead rate is the same. Then the fixed cost carried in stock does not change.