Fixed, Variable and Mixed Costs: A Simple Business Example

A factory doubles production, yet its rent remains unchanged. Material spending rises, while a utility bill contains both a standing charge and usage. These costs behave differently. Recognising that difference helps explain profit and prevents misleading pricing or break-even calculations.

Define the activity and time period

Ask what is changing: units produced, batches, machine hours, deliveries or customers served. Then choose a period and an operating range. A monthly rent can be fixed for the next month but change when a lease expires. A setup charge may stay the same for a batch while total setup cost rises with the number of batches.

A fictional unit-cost comparison

Assume monthly rent is ₹30,000 and variable material cost is ₹80 per unit. The factory can produce either 1,000 or 2,000 units without extra rent or other step costs. Ignore all other costs solely for this illustration.

The second case costs ₹80,000 more in total, but average included cost falls from ₹110 to ₹95 because the same rent is spread over more units. This is not evidence that producing more will always increase profit: selling prices, demand, unsold stock, capacity and other costs still matter.

Do not confuse behaviour with traceability

Direct means a cost can be traced economically to the chosen product, job or activity. Variable describes how it changes with activity. A salaried person dedicated to one department can be direct to that department and fixed over the month. Shared power can be indirect to one product while having a usage-driven component. See CAS-1: Classification of Cost for those separate dimensions.

Use the classification for the right decision

Contribution analysis subtracts the relevant variable costs from revenue, leaving an amount to cover fixed costs and profit. A full cost statement can include allocated fixed costs for a different purpose. Do not mix a full cost per unit containing rent with a contribution calculation that subtracts the same rent again.

For one additional order, ask which future cash flows change, whether extra fixed costs arise and whether another opportunity is displaced. For long-term pricing, examine how the business covers its overall cost base. Neither “all fixed costs are irrelevant” nor “every allocated cost changes with this order” is a safe general rule.

Questions that often come up

Are wages always variable? No. Review employment terms, overtime and staffing thresholds. The relationship may differ across employees and periods.

Is depreciation always a cash payment this month? No. It is an allocation of asset cost. Cash investment and depreciation affect decisions and reports differently.

Can I estimate behaviour from two months alone? Treat that cautiously. Price changes, seasonality, product mix, maintenance and abnormal events can distort the comparison.

Your next practical step

Classify your ten largest costs using an activity, time period and operating range for each. Document uncertainty, then test the classification against actual records before relying on it for a major quote or expansion decision.