Fixed cost

Before you rely on it

What to check

Identify the volume at which the next step happens, then check whether your plan crosses it.

The common error

Where people go wrong with fixed cost

Modelling growth on a single fixed-cost figure. The model shows margins expanding smoothly forever, and reality delivers a step change in the quarter the second location opens.

Worked through

Fixed cost in plain numbers

A workshop pays $3,000 a month in rent no matter what it produces. Make 500 units and the rent adds $6 to each. Make 1,000 and it adds $3. The cost did not change. It spread across more units, which is why growth improves margins when costs are fixed. But fixed does not mean fixed forever. If demand climbs past what one machine can handle, say 1,200 units, the shop must buy a second machine and add $2,000 a month. Costs step up in blocks. Inside a range of output, a fixed cost stays flat. Outside it, it behaves like a new decision.

Easily confused

Fixed cost and its neighbours

A fixed cost is the counterpart of a variable cost, and there is a middle ground. Fixed costs do not change with volume in the short run: rent, salaries, insurance, loan payments. Variable costs rise with each unit: materials, packaging, sales commissions. Semi-variable, or mixed, costs have both parts, like a phone plan with a base fee and usage charges. Sunk costs are past spending that cannot be recovered and should not influence a decision. Overhead is often mostly fixed but is not the same thing.

In real decisions

Where fixed cost turns up

Fixed costs drive break-even analysis. Dividing them by the contribution margin per unit gives the volume needed to reach zero profit; owners use them to judge operating leverage: a business with high fixed costs sees profit swing sharply as sales change; lenders study them to see whether revenue can cover commitments in a slow period. Managers look for fixed costs that can be turned into variable ones, such as renting instead of buying, to reduce risk.

Know the edges

Where fixed cost stops being reliable

Few costs are fixed over long periods. Rent renews, salaries change and capacity limits force steps. Classifying costs is a judgment, and some are mixed. Treating a cost as fixed can lead to poor decisions if it could be avoided by a change. Review the classification when volume moves far beyond the range you assumed, and check contract terms for what really is committed.

Quick answers

What people ask about fixed cost

Are salaries fixed costs? Usually yes in the short run, since they do not change with output. Overtime, commissions and hourly labor tied to volume behave like variable costs.

Why do fixed costs matter for pricing? They must be covered by contribution from sales. If volume is too low, per-unit prices have to be higher or the business loses money.

Can a fixed cost become variable? Yes, through choices like outsourcing, renting equipment by the hour or paying commissions instead of salaries. That reduces risk and may raise cost per unit.

How do fixed costs affect risk? The more of your costs are fixed, the more your profit swings with sales. High fixed costs magnify gains in good times and losses in bad ones.