Business Guides
Part of the CalcProMaster guides library · Updated September 2026
Business math fails most often in the same two spots: confusing margin with markup, and guessing break-even instead of computing it. These guides nail both.
Business maths rewards being explicit about which base a number is divided by: the same profit can be a 20% margin or a 25% markup, and a break-even point is only as honest as the fixed costs that went into it.
How the math works
Margin vs markup is a base confusion: margin is profit ÷ selling price, markup is profit ÷ cost. The same $10 profit on a $40-cost item selling at $50 is a 20% margin and a 25% markup — both correct, answering different questions. Pricing from a target margin needs the markup conversion: price = cost ÷ (1 − margin), so a 30% margin on $70 cost means $100, not $91.
Break-even converts that into planning: units = fixed costs ÷ (price − variable cost per unit). The denominator — contribution margin — is what each sale adds toward covering rent and salaries. The break-even guide runs a full café example, extends it to a target profit, and shows why a business below break-even loses money at roughly the contribution margin per unit, not at its full selling price.
One more distinction the guides keep returning to: profit is not cash. A profitable sale paid on 60-day terms still leaves payroll due on the 30th — which is why the break-even arithmetic a café needs is monthly, in cash terms, not annual. When you run the calculators, feed them the numbers from a real month (rent, average ticket, variable cost per order) rather than aspirational ones; the resulting break-even is then a line you can actually watch the business cross.
Break-Even Analysis — Formula & Margin of Safety
Fixed vs variable costs, contribution margin, a full café example, margin of safety, and the target-profit extension.
Related guides
What this category covers
Break-even, margin, markup, pricing, runway, invoice factoring and unit economics. These are the numbers a small business needs weekly, and the ones most often calculated once and never updated.
Pick the cadence first: margin per sale, break-even per month, runway per quarter. A number with no review rhythm stops being a decision tool.
Fixed and variable costs behave differently
A variable cost moves with each sale and belongs in the contribution margin. A fixed cost is paid whether or not you sell anything, and belongs in the break-even denominator. Putting rent into the per-unit cost makes every unit look unprofitable at low volume.
Some costs are step-fixed: they jump at a threshold, such as a second employee or a larger warehouse. Model them as steps rather than as smooth growth.
Cash is not profit
Profit is recognised when work is done; cash arrives when the customer pays. A profitable month on 60-day terms can still miss payroll, which is why a cash-flow forecast sits beside the profit calculation.
Runway is the more useful number for a young business: months of cash at the current burn. It converts a vague worry into a deadline you can plan against.
Where these answers go wrong
- Using revenue and cost as if they were the same base — margin divides profit by the selling price, markup divides it by the cost, so 20% margin is a 25% markup.
- Leaving fixed costs out because they are paid monthly while the price is per unit — convert both to the same period before dividing.
- Treating profit as cash, which is why a profitable month on 60-day invoice terms can still miss a payroll run.
- Wanting a target margin but applying a markup percentage, which quietly underprices every sale.
Frequently asked questions
Should I price with margin or markup?
Use margin to judge a sale (profit as a share of the price you charged) and markup to price off cost (profit as a share of what you paid). Pricing from a target margin is the safer habit: price = cost ÷ (1 − margin), so a 30% margin on a $70 cost is $100, not $91.
Does break-even include tax?
Break-even as normally written covers operating costs only, so it is a pre-tax line. Profit tax is charged on profit, not on the point where profit becomes zero, so folding it into the break-even calculation would double-count it. Keep the two questions separate and apply tax afterwards.
Why does my spreadsheet disagree with a break-even calculator?
Almost always one of three inputs: rounding of contribution margin per unit, whether owner pay and loan repayments sit in fixed costs, or a different period. Put every figure on the same monthly or annual basis, list what is and is not counted, and then compare the two results.
Worked example: Break-Even Calculator at its default inputs
Take the default setup on Break-Even Calculator: no fields changed, nothing tuned to a nice round number. Run in the site's own engine, those values produce the answer below.
| Input | Default |
|---|---|
| Fixed Costs | 10000 |
| Price per Unit | 50 |
| Variable Cost/Unit | 20 |
Result: Break-Even: 333 units
The steps behind that answer
- Formula: Break-Even = Fixed Costs / (Price - Variable Cost)
- Step 1: Contribution margin = $50 - $20 = $30
- Step 2: Break-even = $10000 / $30 = 333 units
Fixed Costs — three values, three answers
Same calculator, same fields, one change: fixed costs.
| Fixed Costs | Result |
|---|---|
| 5,000 | Break-Even: 167 units |
| 10,000 | Break-Even: 333 units |
| 15,000 | Break-Even: 500 units |
Read the three rows as a range: the spread between them is how much the answer depends on fixed costs alone, with everything else held still.
Try the matching calculators
Break-Even Calculator Profit Margin Calculator Loan EMI Calculator
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