How the Cost of Doing Business Calculator works
Running a business means paying two kinds of costs: costs that stay the same no matter how much you sell (fixed costs) and costs that rise and fall with volume (variable costs). This calculator adds the two together to get your total cost of doing business, then compares that total to your revenue to show your cost-to-revenue ratio, net profit, and the break-even volume — the point where sales exactly cover costs.
The formula
For annual Fixed Costs, a Variable Cost per Unit, a Selling Price per Unit, and Units Sold, the calculator applies standard cost-volume-profit (break-even) analysis:
Total Cost = Fixed Costs + (Variable Cost per Unit × Units Sold)
Total Revenue = Selling Price per Unit × Units Sold
Cost-to-Revenue Ratio (%) = Total Cost / Total Revenue × 100
Net Profit = Total Revenue − Total Cost
Break-Even Units = Fixed Costs / (Selling Price per Unit − Variable Cost per Unit)
The denominator of the break-even formula — price minus variable cost — is the contribution margin per unit: what each additional sale contributes toward covering fixed costs once its own variable cost is paid. Fixed costs typically include items like rent, salaried wages, insurance, and administrative overhead; variable costs typically include materials, hourly labor tied to output, packaging, and per-unit shipping or commissions.
Worked example
Take $50,000 in annual fixed costs, a variable cost of $15 per unit, a selling price of $25 per unit, and 5,000 units sold in a year. Total cost is $50,000 + ($15 × 5,000) = $125,000. Total revenue is $25 × 5,000 = $125,000, so the cost-to-revenue ratio is exactly 100% and net profit is $0 — this business is precisely at break-even. The contribution margin is $25 − $15 = $10 per unit, so break-even units = $50,000 / $10 = 5,000 units, matching the units actually sold.
What moves the result most
- Fixed costs: a higher fixed-cost base raises total cost by the same amount at every volume and pushes the break-even point higher, since more units are needed to cover it.
- Contribution margin (price minus variable cost): a thin margin means a large number of units is needed to break even; a wide margin lets fewer units cover the same fixed-cost base.
- Units sold: selling above break-even volume turns the contribution margin on every extra unit into profit; selling below it leaves fixed costs only partly covered, producing a loss.
Limits of this model
This calculator assumes variable cost per unit and price per unit stay constant across the full range of volume entered — it does not model bulk-discount pricing, step-changes in fixed costs (like leasing a second facility), or taxes. Use it as a transparent first pass on unit economics, then layer in financing costs, taxes, and pricing strategy separately for a full business plan.