What it means
Every business spends money, but not all expenses react the same way when business gets busier or slower. Some expenses stay completely flat no matter how much you sell, while others rise and fall in direct proportion to your sales activity.
Separating these costs is vital for accurate budgeting and forecasting. Expenses generally fall into three main buckets: fixed, variable, and mixed.
Fixed costs, like your monthly office rent, remain unchanged regardless of your output. Variable costs, such as raw materials, increase as you produce more items because each sale requires more inputs.
Mixed costs contain elements of both, such as a utility bill with a base connection fee plus usage charges. For non-finance managers, knowing how costs behave prevents nasty surprises.
If you assume all costs are fixed, a surge in sales might leave you short of supplies. Conversely, if you think all costs scale with sales, you might misjudge your profit margins.
Analysing cost behaviour allows you to calculate your break-even point and make confident decisions about pricing and expansion.
In practice
Real-world examples.
Example
As a freelance graphic designer, your monthly website hosting software fee is a fixed cost of 30 pounds, while printing costs for client brochures rise by 5 pounds for every job you complete.
Example
For a local bakery, the monthly oven lease is a fixed cost of 800 pounds, whereas the flour, butter, and sugar costs go up by 2 pounds for every loaf of bread baked and sold that week.
Example
A regional courier company pays 2,000 pounds per month for vehicle insurance, while fuel costs rise and fall depending on the total distance driven by drivers making daily deliveries.
Think of it
“Think of a mobile phone plan. Your monthly line rental is a fixed cost that you pay even if you make zero calls. The extra charges for data overages represent variable costs that grow the more you use them.
Formula
Calculation
Total Cost = Fixed Costs + (Variable Cost per Unit x Number of Units)
Example: If your bakery has fixed monthly rent of 1,000 pounds, and it costs 2 pounds of ingredients to bake a cake, making 500 cakes results in:
Total Cost = 1,000 + (2 x 500)
Total Cost = 1,000 + 1,000 = 2,000 pounds.Case study
Seen in the real world.
GreenLeaf Candles, a growing manufacturer, needed to understand its expenses to survive a busy winter season. The manager reviewed the books and separated costs. Rent and salaries totalled 5,000 pounds per month, remaining completely flat whether they made 100 or 1,000 candles. Meanwhile, wax and wicks cost 3 pounds per candle produced. By understanding this behaviour, GreenLeaf calculated that producing 1,000 candles would cost 5,000 pounds in fixed expenses plus 3,000 pounds in variable expenses, giving a total cost of 8,000 pounds. This clear insight allowed the team to price each candle at 12 pounds, ensuring a healthy profit margin of 4 pounds per unit once fixed costs were fully covered.
Watch out
Common mistakes.
- Assuming all business expenses are entirely variable and will drop to zero if sales stop.
- Treating fixed costs as a per-unit figure that stays the same regardless of production volume.
- Ignoring mixed costs and failing to separate them into their fixed and variable components.
Questions
People also ask.
Why is understanding cost behaviour important for pricing?
It shows you the exact cost of producing one more unit of your product, helping you set a price that covers both variable production costs and a share of your fixed overheads.
Are fixed costs truly fixed forever?
No. Fixed costs are only fixed within a certain range of business activity. If your sales double, you may need a larger warehouse, which increases your fixed rent.
How do I handle mixed costs in my budget?
You must split mixed costs into their fixed and variable parts using past data, separating the base fee from the usage-based portion.
From the founder's library
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