Fixed vs variable costs

Definition

Fixed costs are expenses that do not change with how much you produce or sell over a given period — rent, salaried staff, insurance, software subscriptions. You pay them whether you sell one unit or a thousand. Variable costs move directly with output: raw materials, hourly or piece-rate labour, packaging, delivery, card-processing fees. The more you make or sell, the more they total. Most businesses carry a blend of the two, and a few costs are “semi-variable” — a fixed base plus a usage element, like a phone plan.

In plain terms

Picture switching the business off for a quiet month with no sales at all. The costs that still land on your desk — the lease, the salaries, the insurance — are fixed. The costs that vanish because you produced nothing — the materials, the delivery charges — are variable. Knowing which is which tells you how much it costs simply to keep the doors open, and how much each extra sale genuinely adds to your costs. That second figure is what feeds your contribution margin.

Why it matters to your business

The mix of fixed and variable costs determines your break-even point and how exposed you are to a downturn. A business heavy on fixed costs has a high break-even — it must sell a lot just to cover the overheads — but once past it, profit climbs fast because extra sales carry low variable cost. A business weighted toward variable costs has a lower break-even and more flexibility when sales fall, since costs shrink with revenue, but it gives up less of that explosive operating leverage on the way up. Neither is right or wrong; the question is whether your cost structure matches how stable your sales are.

• Fixed-heavy: high break-even, big upside, more risk in a slump
• Variable-heavy: lower break-even, flexible, gentler upside
• The right mix depends on how predictable your sales are

The role in break-even and resilience

Break-even is simply the point where total contribution covers total fixed costs. The higher your fixed costs, the more units you must sell to reach it — which is why a sudden drop in revenue hurts a fixed-heavy business so sharply. When demand is uncertain, converting fixed costs into variable ones (outsourcing instead of hiring, leasing instead of buying) builds resilience, because your costs then fall in step with your sales. Funding can play a part too: asset finance spreads a large fixed purchase into manageable instalments, and a flexible facility covers the gap when fixed costs fall due before the cash arrives.