What Are Variable Costs?

Variable costs are expenses that change in direct proportion to the volume of goods produced or services delivered. When output increases, total variable costs rise; when output falls, they decrease. The variable cost per unit remains approximately constant.

Understanding variable costs is essential for break-even analysis , pricing decisions, budgeting , and management accounting . Together with fixed costs , they determine the total cost structure of a business.

Examples of Variable Costs

Variable Costs Versus Fixed Costs

Calculating Total Variable Cost

Total Variable Cost = Variable Cost Per Unit x Number of Units

Worked Example

A bakery produces loaves of bread with the following variable costs:

If the bakery produces 10,000 loaves in a month:

Total Variable Cost = £1.45 x 10,000 = £14,500

If production increases to 15,000 loaves:

Total Variable Cost = £1.45 x 15,000 = £21,750

The cost per loaf stays at £1.45, but total variable costs increase by £7,250.

Variable Costs and Contribution Margin

The contribution margin is the difference between the selling price and the variable cost per unit:

Contribution Per Unit = Selling Price - Variable Cost Per Unit

This contribution first covers fixed costs and then generates profit. It is the foundation of break-even analysis.

Using the bakery example, if each loaf sells for £3.00:

Contribution Margin Ratio = £1.55 / £3.00 = 51.7%

For every £1 of turnover, 51.7p contributes toward fixed costs and profit.

Variable Costs on the Income Statement

In a standard UK income statement under the Companies Act 2006, costs are classified by function (cost of sales, distribution, administration) rather than by behaviour. Variable costs are spread across these categories:

For internal management accounting purposes, a marginal costing income statement separates costs by behaviour:

This format makes the contribution and the impact of volume changes immediately visible.

Semi-Variable Costs

Some costs have both fixed and variable elements:

For break-even and budgeting purposes, semi-variable costs must be split into their fixed and variable components. The high-low method is a simple technique:

Variable Rate = (Highest Total Cost - Lowest Total Cost) / (Highest Activity - Lowest Activity)

Example

Variable Rate = (£3,600 - £2,400) / (14,000 - 8,000) = £0.20 per unit

Fixed Element = £2,400 - (8,000 x £0.20) = £800 per month

Reducing Variable Costs

Reducing variable costs per unit lowers the break-even point and increases the contribution margin, directly improving profitability.

Variable Costs and Pricing

Marginal Cost Pricing

In the short term, a business can accept orders at any price above variable cost because each sale makes a positive contribution. This is called marginal cost pricing and is used when:

• The business has spare capacity
• The order does not displace higher-margin sales
• The customer will not expect the low price permanently

However, in the long term, prices must cover both variable and fixed costs to sustain the business.

Full Cost Pricing

Full Cost Per Unit = Variable Cost Per Unit + (Total Fixed Costs / Expected Units)

Using the bakery example with fixed costs of £15,000 per month and expected production of 10,000 loaves:

The selling price of £3.00 gives a profit margin of £0.05 per loaf (1.7%), which may prompt a review of pricing or cost structure.

Variable Costs and Corporation Tax

Variable costs are fully deductible for corporation tax purposes as trading expenses, provided they are incurred wholly and exclusively for the purposes of the trade. There are no special tax adjustments for variable costs – the distinction between variable and fixed is a management accounting classification, not a tax one.

However, the stock valuation for tax purposes must include both variable production costs and a fair proportion of fixed production overheads under the absorption costing requirement of FRS 102 Section 13. Using marginal costing to value stock (excluding fixed overheads) is not permitted for statutory or tax accounts.

Variable Costs in Different Sectors

Businesses with lower variable costs as a percentage of turnover have higher contribution margins and reach break-even at lower sales volumes, but they typically have higher fixed costs (salaries, technology, premises).