Cleaner

Difference = selling price − entered cost. Margin = difference ÷ selling price × 100; markup = difference ÷ cost × 100. A zero denominator is undefined. Percentages round to 2 decimals. Use the same unit and cost basis. The difference is not net profit: omitted labour, materials, overhead, fees and taxes are not inferred. Arithmetic only, not a price recommendation.

For a single product or service: contribution per unit = price − variable cost. When contribution is positive, whole units = fixed costs ÷ contribution, rounded UP without intermediate rounding. Revenue = whole units × price; total entered cost = fixed costs + whole units × variable cost. With positive fixed costs, zero or negative contribution has no finite break-even target. With zero fixed costs, zero sales already cover the entered costs; if contribution is also zero, every quantity balances. No numeric target is returned for these nonpositive-contribution cases. Keep all fixed costs in the same period; use one consistent unit, such as one visit or meal. Enter all applicable variable costs, including labour and materials, without double-counting fixed costs. Prices, unit costs and fixed costs are assumed constant; capacity, demand, timing of payments and tax rules are not modelled. No taxes, contingency or rates are added. This is not a profit or cash-flow forecast.