Variable cost

Published Thursday 23 July 2026

Table of contents

• What is a variable cost?
• Examples of variable costs
• How to calculate variable costs
• Why variable costs matter
• How variable costs differ from fixed and semi-variable costs
• What are stepped costs?
• How to manage variable costs
• Stay on top of your variable costs with Xero
• FAQs on variable costs
• Related terms
• Learn more about variable costs

Key takeaways

• Variable costs rise and fall in line with how busy your business is, so they're the opposite of fixed costs.
• You work out your total variable cost by multiplying the number of units by the variable cost per unit.
• Tracking variable costs helps you set prices, protect your margins and plan your cash flow with more confidence.
• Reviewing suppliers and using accounting software to monitor costs makes variable costs easier to manage as you grow.

What is a variable cost?

A variable cost is an expense that goes up and down in line with your business activity: the busier you are, the higher it goes. Variable costs are the opposite of fixed costs, which stay the same no matter how much you sell.

Many variable costs, such as inventory and freight, move up in line with the number of sales you make. Not every variable cost syncs up this neatly, though. Spending on marketing, trade shows and sales travel is meant to drive sales, but it won't always match your sales figures exactly.

Examples of variable costs

Variable costs show up across most parts of a small business, usually wherever spending is tied to how much you produce or sell. Here are some common examples you'll recognise.

• Inventory and raw materials that go into the products and services you offer
• Packaging and shipping for those goods
• Transaction fees for accepting payments by card, digital wallet and direct debit
• Contractors you hire during busy periods
• Marketing, which rises and falls depending on when you run campaigns
• Sales travel, which increases when your reps go on the road
• Commissions and referral bonuses paid on sales

How to calculate variable costs

Working out your variable costs helps you understand what each sale really costs you. The calculation is simple once you know your cost per unit.

Your total variable cost is the number of units you make or sell multiplied by the variable cost per unit:

• Total variable cost = number of units × variable cost per unit
• Variable cost per unit = total variable cost ÷ number of units

Say you run a candle business and each candle costs you $6 in wax, wicks, fragrance and packaging. If you make 500 candles in a month, your total variable cost is 500 × $6, which comes to $3,000. If output rises to 700 candles the next month, your total variable cost climbs to $4,200, while the cost per unit stays at $6.

Why variable costs matter

Variable costs change from week to week and month to month, depending on what your business is doing. That makes them trickier to budget than fixed costs, and it makes them worth watching closely.

A clear view of your variable costs helps you in several practical ways. You can build more accurate budgets, set prices that protect your profit margins, and work out your break-even point (the sales level where your income covers your costs). It also helps you predict your cash flow, so you know how much you'll need on hand as sales rise and fall.

How variable costs differ from fixed and semi-variable costs

Not every cost behaves the same way as activity changes. Sorting your costs into the right group makes them easier to plan for.

A fixed cost stays the same no matter how active your business is. Fixed costs include things like rent, insurance, and permanent wages and salaries. A variable cost, by contrast, moves with your output, so the two behave in opposite ways.

Some costs sit in between and are known as semi-variable or mixed costs. A semi-variable cost has a fixed base plus a usage component that changes with activity. A mobile phone plan is a good example: you pay a set monthly fee, then extra charges once you go over your data or call allowance.

What are stepped costs?

Variable costs don't always rise in a smooth line as you grow. Sometimes they jump in larger amounts, and these are called stepped costs.

Some variable costs go up in direct proportion with business activity. Inventory costs, for example, often rise in step with sales. In other cases the relationship isn't so linear.

A busy business might hire a new employee who can make another 200 products. The wage cost jumps significantly, but it opens the door to another 200 sales. Variable costs that move in these larger jumps are known as stepped costs.

How to manage variable costs

Because variable costs shift with activity, small changes can add up quickly across a year. A few regular habits help you keep them under control.

• Review your suppliers and prices regularly to make sure you're still getting a fair deal
• Use accounting software to track your costs in real time rather than at year end
• Watch your cost per unit as you scale, so growth doesn't quietly eat into your margins
• Negotiate bulk or volume rates with suppliers once your order sizes grow

Stay on top of your variable costs with Xero

Keeping an eye on variable costs is far easier when your numbers are all in one place and updated as you go. Xero brings your income and spending together so you can spot rising costs early and act on them.

With online accounting software you can track expenses, monitor your cash flow and see how each cost affects your margins, so you can see where your money goes and get one month free.

FAQs on variable costs

Here are answers to some frequently asked questions about variable costs to help you put the ideas above into practice.

How do you calculate variable cost?

Multiply the number of units you make or sell by the variable cost per unit. So if you produce 300 units at $4 each, your total variable cost is $1,200.

What's the difference between fixed and variable costs?

Fixed costs stay the same regardless of activity, like rent or insurance. Variable costs rise and fall with how much you produce or sell.

What is variable cost per unit?

It's the variable cost of making a single unit, found by dividing your total variable cost by the number of units. It usually stays steady even as your total output changes.

Is labour a fixed or variable cost?

It depends on the role: permanent salaried staff are usually a fixed cost, while casual or contract workers you bring in during busy periods are a variable cost. Commission-based pay also counts as variable.

Are variable costs the same as direct costs?

They often overlap but aren't identical: direct costs are tied to a specific product, while variable costs are tied to activity levels. A cost can be both, such as the raw materials in a single product.

Related terms

• Fixed cost
• Expense
• Overhead
• Cost of sales
• Break-even point

Learn more about variable costs

• Calculating marginal cost
• What are overheads?
• Cost of sales calculation
• What is gross profit margin?