Variable costs change directly with production or sales volume — raw materials, hourly labor, commissions, and shipping are typical examples. They scale proportionally with revenue.
Variable costs are the costs of actually doing business — they arise because the business is producing or selling. A manufacturer pays for materials only when it builds products. A staffing agency pays temp worker wages only when placements are active. A delivery service pays fuel and driver pay proportional to deliveries made. Pure variable costs are linearly proportional to volume. In practice, many costs that appear variable have semi-variable components — a delivery driver's base pay is fixed, but fuel is variable; a production worker has a minimum-hours guarantee that is partly fixed. These are sometimes called 'mixed costs' or 'semi-variable costs.' The variable cost ratio (variable costs / revenue) drives contribution margin. If variable costs are 55% of revenue, contribution margin is 45% — meaning every additional dollar of revenue contributes 45 cents toward fixed costs and profit. Businesses with low variable cost ratios (software, financial services) have high contribution margins and scale economics. Businesses with high variable cost ratios (distribution, commodity manufacturing) are more volume-sensitive. During financing analysis, lenders model revenue scenarios and apply the variable cost ratio to estimate operating income under stress. A business with high variable costs contracts more predictably when revenue falls — it's not stuck with large fixed obligations.
COGS (cost of goods sold) is a category on the income statement that includes the direct costs of production or service delivery — often a mix of variable and semi-fixed costs. Variable costs are an analytical concept (costs that scale with volume). COGS typically includes the most variable costs (materials, direct labor) but may also include fixed manufacturing overhead allocated per unit under absorption costing.
Lower variable costs = higher contribution margin per unit = faster fixed-cost recovery and more profit per additional sale. Businesses scale more efficiently with low variable costs. However, shifting costs from variable to fixed (e.g., hiring full-time instead of contractors) increases operating leverage — more upside but more downside risk.
Variable costs typically require cash outflow close to or before the sale. Materials are purchased (cash out) before product is sold (cash in). This creates working capital requirements. Businesses with high variable costs and slow-paying customers often need working capital financing to bridge the gap.