Fixed vs variable costs: Understanding your business expenses
Learn the difference between fixed vs variable costs, with plain UK examples and a simple break-even guide.
Written by Naomi Lai— Small business & finance writer. Read Naomi's full bio
Published Wednesday 23 September 2026
Table of contents
Key takeaways
- Fixed costs stay the same each period no matter how much you sell, such as rent, business insurance, and salaries.
- Variable costs rise and fall with how much you produce or sell, such as materials, packaging, and card fees.
- Knowing which costs are which helps you set prices, plan a budget, and work out your break-even point.
- Most businesses also have semi-variable costs that mix a fixed base with a usage-based part.
What are fixed costs?
Some bills land at the same amount every month, whether trade is busy or quiet. These steady payments are the first group to get straight.
Fixed costs stay the same each period regardless of how much you sell. You pay them even in a month when you sell nothing, which makes them the baseline of your outgoings.
These are examples of common fixed costs for a UK small business:
- Rent: the monthly charge for your shop, unit, or office
- Business rates: the tax you pay to your local council on many commercial premises
- Business insurance: cover such as public liability or contents insurance
- Permanent staff salaries: fixed pay for employees on a set wage
- Software subscriptions: monthly or yearly fees for the tools you use
- Loan repayments: set repayments on a business loan or finance agreement
Fixed costs can still change over time. Your landlord might raise the rent at a review, or an insurer might adjust your premium. They just don't move up and down with your sales. You can check what you owe on premises using the official business rates guidance on GOV.UK.
What are variable costs?
The next group behaves in the opposite way, growing when you're busy and shrinking when trade slows. Variable costs rise and fall with how much you produce or sell. Sell twice as much, and they roughly double, and if you sell nothing, they drop close to zero.
Here are examples of common variable costs for a UK small business:
- Materials and stock: the goods or ingredients you buy to sell
- Packaging: boxes, bags, and labels for your products
- Delivery and postage: courier or Royal Mail charges for sending orders
- Payment processing fees: the percentage a card provider takes per sale
- Hourly or casual wages: pay for staff whose hours flex with demand
- Commission: a cut paid to salespeople on what they sell
Because they follow your activity, variable costs are often measured per unit, meaning the cost to make or sell one item. That figure matters later when you work out your break-even point.
Fixed vs variable costs: What's the difference?
Both cost types are normal parts of running a business, and most firms carry a mix of the two. The simplest way to tell fixed versus variable costs apart is to ask whether the bill moves when your sales move.
Fixed costs behave like this:
- Behaviour: stay flat no matter how much you sell
- Predictability: easy to forecast from one month to the next
- Per unit: the cost per item falls as you sell more
- Control: harder to change quickly, since many are tied to contracts
Variable costs behave like this:
- Behaviour: go up and down with your output or sales
- Predictability: harder to forecast, as they follow demand
- Per unit: the cost per item stays roughly the same
- Control: easier to adjust in the short term by changing what you buy
As you sell more, your fixed cost per unit gets smaller because you're spreading the same bill across more sales. Your variable cost per unit tends to hold steady.
What are semi-variable costs?
Not every cost fits neatly into one box. Some bills have a foot in both camps, so spotting them keeps your figures accurate. A semi-variable cost has a fixed base plus a variable part that changes with use. You pay a set amount no matter what happens, then more on top the more you use.
These are typical UK examples:
- Utilities: a fixed standing charge for gas or electricity, plus a charge for what you use
- Phone and mobile plans: a set monthly fee, plus extra for calls or data over your allowance
- Staff pay with overtime: a fixed salary, plus variable overtime in busy spells
To handle a semi-variable cost, split it into two parts. Record the fixed base with your other fixed costs and treat the usage part as variable. That keeps your planning clean and stops a mixed bill from throwing off your sums.
How to work out your fixed and variable costs
Sorting your costs is a straightforward job you can do in an afternoon. Work through these five steps and you'll have a clear map of where your money goes.
1. List every business expense
Write down every business expense, from rent and wages to stock, postage, and software. A bank statement or your accounting records make a handy checklist so nothing slips through.
2. Ask if each cost changes with sales
Take each expense in turn and ask one question: Does this bill go up when I sell more? If the answer is no, it leans fixed. If yes, it leans variable.
3. Group them into fixed, variable, and semi-variable
Sort your list into three columns: fixed, variable, and semi-variable. Most costs will fall clearly into fixed or variable, with a few landing in the middle.
4. Split any semi-variable costs
For each semi-variable cost, separate the fixed base from the usage part. Put the standing charge with your fixed costs and the usage with your variable costs.
5. Review the list regularly
Costs shift as your business grows, so revisit your list every few months. A new supplier, a rent review, or a change in VAT can all move the numbers.
Here's how that looks in practice. Imagine a small café with £2,000 in fixed costs each month for rent, business rates, and insurance. Ingredients and takeaway cups are variable, at about 90p for every £3 coffee sold. Sell 1,500 coffees in a month, and variable costs come to £1,350 on top of the £2,000 that stays fixed.
Why the difference matters for your business
Telling your costs apart isn't just an accounting exercise. Your cost structure shapes almost every money decision you make, so a clear split gives you real control.
Knowing your fixed and variable costs helps you in these ways:
- Set prices. Make sure each sale covers its variable cost and helps pay your fixed bills.
- Build a budget. Use fixed costs as a steady baseline and flex the variable side around it.
- Protect cash flow. Spot when high fixed costs could squeeze you in a slow month.
- Decide when to scale. Understand how costs will grow before you take on more work.
- Find savings. Target the costs you can adjust quickly when money is tight.
Cash flow deserves special attention here. A business with high fixed costs needs steady sales to stay comfortable, so watch your cash flow position closely when trade dips.
How fixed and variable costs affect your break-even point
Once you know your costs, you can answer a question every owner asks: How much do I need to sell to cover everything?
Your break-even point is where total sales equal total costs, so you make neither a profit nor a loss. A break-even analysis puts a real number on it, which helps you set targets and judge whether a price works.
The break-even formula is:
break-even units = fixed costs ÷ (price per unit − variable cost per unit)
The gap between your price and your variable cost per unit is what each sale contributes towards fixed costs. Say your café has £2,000 in monthly fixed costs, sells coffee at £3, and spends 90p per takeaway cup. Each coffee contributes £2.10, so you divide £2,000 by £2.10 and need to sell about 953 coffees a month to break even.
The break-even analysis guidance from the Federation of Small Businesses goes further. Lower fixed costs or a wider margin per unit both pull your break-even point down. Classifying your costs pays off because it feeds straight into targets you can plan around.
Manage your business costs with Xero
Sorting fixed and variable costs is far easier when your figures live in one place instead of a pile of receipts. Accounting software tracks every expense as it happens, so you can group costs, watch trends, and see where your money goes without the manual admin.
With clear reports and up-to-date numbers, you can review your cost structure, test prices, and check your break-even point whenever plans change. See how simple staying on top of costs can be, with online invoicing tools that help money come in as reliably as it goes out.
FAQs on fixed and variable costs
Here are quick answers to the questions small business owners ask most about sorting their costs.
Is rent a fixed or variable cost?
Rent is a fixed cost because you pay the same amount each period whether sales are high or low. It can change at a rent review, but never because you sold more or less.
Is a salary a fixed or variable cost?
A set salary is a fixed cost, since the amount stays the same regardless of output. Hourly or casual pay that rises with demand counts as a variable cost instead.
Are utility bills fixed or variable costs?
Utility bills are usually semi-variable, with a fixed standing charge plus a variable amount based on how much energy you use. Split them into both parts for accurate planning.
What are examples of variable costs?
Common variable costs include materials and stock, packaging, delivery, card payment fees, commission, and hourly wages. Each rises and falls with how much you sell.
Can a cost be both fixed and variable?
Yes, and that mix is a semi-variable cost, such as a phone plan with a set fee plus charges for extra use. You treat the fixed base and the variable part separately.
Why do fixed and variable costs matter for pricing?
Your price needs to cover the variable cost of each sale and still contribute towards your fixed costs. Knowing both figures stops you from setting a price that quietly loses money.
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