Profit margin is your profit divided by the price the buyer pays, expressed as a percentage. Break-even is the point where total contribution from sales exactly covers your fixed costs. To price for a target margin when fees are involved, add up every per-unit cost, then divide by what remains after the percentage fees and the target margin are taken out of the price: price before discount = (fixed per-unit fees + all per-unit costs) ÷ (1 − payment % − platform % − target margin), and divide by (1 − discount rate) if you also plan a discount. Our free Pricing and Break-Even Simulator runs this calculation with every formula shown, compares up to three scenarios side by side, and exports the result. This guide derives the formulas, works one complete example with real arithmetic, and then shows the scenario sellers least want to see: a price at which break-even does not exist.
The definitions, kept separate
Three terms are routinely confused, and the confusion costs money:
- Profit (per unit) = amount the buyer pays − all per-unit costs, including percentage fees.
- Margin = profit ÷ price the buyer pays. Margin is always a share of the price.
- Markup = profit ÷ cost. Markup is always a share of the cost.
A worked micro-example keeps them apart. If an item costs $20.00 all-in and sells for $25.00, profit is $5.00, margin is $5.00 ÷ $25.00 = 20%, and markup is $5.00 ÷ $20.00 = 25%. Same product, same profit, two different percentages. Pricing "at a 25% margin" using the markup formula would set the price at $25.00 when a true 25% margin requires $20.00 ÷ (1 − 0.25) = $26.67. Whenever someone quotes you a percentage, ask: of the price, or of the cost?
Contribution margin is the per-unit amount left after variable costs (everything that scales with each sale) to pay fixed costs and then become profit: contribution = price received − variable costs per unit. Break-even units = fixed costs ÷ contribution per unit. These are the standard definitions used in cost-volume-profit analysis (see the OpenStax references) — the rest of this guide is arithmetic built on them.
Every cost belongs in the price
The worked example uses a hypothetical small seller — all figures are illustrative, stated so you can reproduce every step — selling one product online:
| Input | Value | Type |
|---|---|---|
| Unit cost (product itself) | $8.00 | per unit |
| Shipping cost to you | $2.50 | per unit |
| Ad cost per sale | $3.00 | per unit |
| Payment processing fee | 2.9% of amount paid + $0.30 | % + fixed |
| Platform fee | 10% of amount paid | % |
| Planned discount | 10% off list price | reduces amount paid |
| Target margin | 25% of amount paid | goal |
| Fixed costs (monthly) | $1,200 | period cost |
Three assumptions are stated because changing them changes the answer: percentage fees are charged on the discounted amount the buyer actually pays; margin is measured against that same discounted amount; and prices here are tax-exclusive — if your prices include sales tax or VAT, remove the tax portion first, because tax you collect for the government is not revenue (the simulator has a tax-handling option for exactly this reason).
Method note, so the evidence standard is explicit: every figure in this example and in the second scenario below was computed with a small Python script implementing exactly the formulas shown — not read from the finished simulator's screen — and the headline result was then cross-checked with the backward verification table in the next section, which recomputes profit and margin from the rounded price. Where the script's exact result and the rounded-price result differ, both are stated.
Worked example: price for a 25% margin
Per-unit costs that do not depend on price: $8.00 + $2.50 + $3.00 = $13.50, plus the fixed part of the payment fee, $0.30 — together $13.80 that every sale must cover before profit.
Let D be the discounted amount the buyer pays. Three percentage claims are taken out of D: payment 2.9%, platform 10%, and your 25% target margin. What is left of D must cover the $13.80:
D × (1 − 0.029 − 0.10 − 0.25) = 13.80
D × 0.621 = 13.80
D = 13.80 ÷ 0.621 = $22.2222…The buyer must pay $22.22 after discount. Since the discount is 10% off list, the list price is $22.2222 ÷ (1 − 0.10) = $24.6914…, so set the list price at $24.69.
Now verify the rounded price end to end — never trust a formula you have not run backwards:
| Line | Calculation | Amount |
|---|---|---|
| List price | set | $24.69 |
| Buyer pays (after 10% discount) | 24.69 × 0.90 | $22.2210 |
| Payment fee | 22.2210 × 2.9% + $0.30 | −$0.9444 |
| Platform fee | 22.2210 × 10% | −$2.2221 |
| Unit + shipping + ad costs | 8.00 + 2.50 + 3.00 | −$13.5000 |
| Profit per unit (= contribution) | $5.5545 | |
| Margin | 5.5545 ÷ 22.2210 | 25.00% |
The margin lands on target because the rounding cost only a fraction of a cent of profit. Notice how much work the fees and discount are doing: without the discount and ad cost, the same 25% margin target prices the product at ($0.30 + $10.50) ÷ 0.621 = $17.39. The $7.30 gap between $17.39 and $24.69 is the true price of the promotion and the advertising — visible only because both were put inside the calculation instead of discovered afterwards.
Break-even. Contribution per unit is $5.5545, so break-even units = $1,200 ÷ $5.5545 = 216.04…, which rounds up to 217 units per month (at the exact unrounded price it is exactly 216; the price rounding is why you should always round units up — selling the fractional unit is not possible, and rounding down would leave you a few cents short of covering fixed costs). Below 217 units the product loses money that month; above it, each additional unit adds $5.55 of profit.
Break-even ROAS (return on ad spend) follows from the same figures, but keep two different ratios separate. The current ROAS at this example's ad cost is revenue per sale ÷ ad cost per sale = $22.2210 ÷ $3.00 = 7.41× — that is the return the advertising is achieving at $3.00 per sale, not the break-even figure. Break-even ROAS, as the Pricing Simulator defines it, is the amount paid ÷ the profit per unit before ad cost. Profit before ads here is the $5.5545 contribution plus the $3.00 ad cost = $8.5545, so break-even ROAS = $22.2210 ÷ $8.5545 = 2.60×: advertising breaks even as long as each $1.00 of ad spend returns at least $2.60 of revenue at this price. Put the other way round, the product stays above break-even until the ad cost rises above $8.5545 per sale — only past that point does the contribution turn negative. The simulator recomputes break-even ROAS live as you change the ad cost, which is the fastest way to see how much advertising a price can actually carry.
Second scenario: when contribution is zero or negative
Now the honest case. Suppose a competitor forces the price down to $12.99, no discount, with the same costs as above:
| Line | Amount |
|---|---|
| Buyer pays | $12.9900 |
| Payment fee (12.99 × 2.9% + $0.30) | −$0.6767 |
| Platform fee (12.99 × 10%) | −$1.2990 |
| Unit + shipping + ad costs | −$13.5000 |
| Profit per unit | −$2.4857 (margin −19.14%) |
Contribution is negative: every sale loses $2.49 before fixed costs are even considered. The break-even formula returns $1,200 ÷ (−$2.4857), a negative unit count, which is the arithmetic telling you the truth — no break-even point exists at this price. Selling more units loses more money; there is no volume that fixes a negative contribution. The only fixes are structural: raise the price (the formula above says $13.80 ÷ (1 − 0.029 − 0.10) = $15.84 is the lowest discounted price at which contribution reaches exactly zero, and any real margin needs more), cut a per-unit cost, or stop paying $3.00 per sale for ads that deliver $12.99 orders. Any calculator or adviser that shows a break-even chart for a negative-contribution product without flagging this is hiding the most important number on the page.
Assumptions and limits
- Fees are modelled as percentages of the amount paid, plus the stated fixed fee. Real fee schedules have tiers, cross-border surcharges, and refund rules; substitute your actual schedule's numbers — the structure of the calculation does not change.
- Ad cost per sale is an average. It moves with your ROAS daily. Treat the break-even units figure as tied to the ad cost you entered, and re-run it when campaigns change. Costs you spend to get the sale belong per-unit; costs you pay regardless of sales (rent, subscriptions, salaries) belong in fixed costs. Mixing the two is the most common break-even error.
- Tax is excluded by design in the example. If your displayed prices include tax, the taxable-revenue portion is smaller than the sticker price, and margins computed on the sticker price are overstated.
- Rounding is real. Prices end in cents and units are whole; the example shows both the exact and rounded results, and the difference (216 vs 217 units) is the size of error rounding alone can introduce.
Once a price is set, the campaigns that deliver buyers at that ad cost need tracking that survives contact with real reports — see How to Build and Track UTM Parameters. Sellers handling many products in a spreadsheet will also find the row discipline in How to Clean and Transform CSV Files useful, and the simulator exports its scenarios as CSV for exactly that workflow. A final check before publishing any price: run the backward verification table above on your own numbers, because a price you cannot verify by hand is a price you do not understand yet.
Frequently asked questions
What is the difference between margin and markup?
Margin divides profit by the price; markup divides profit by the cost. A $5 profit on a $25 price is a 20% margin and a 25% markup on a $20 cost. They coincide only when profit is zero, which is why the distinction matters most exactly when business is good.
How do I calculate a selling price for a target margin with fees?
Add all per-unit costs that do not depend on price, plus any fixed per-transaction fee. Then divide by (1 − total percentage fees − target margin). If you also offer a discount, divide again by (1 − discount rate) to get the list price. The worked example above shows every step with real numbers.
What is the break-even point formula?
Break-even units = fixed costs ÷ contribution per unit, where contribution = price received − all variable costs per unit. Always round the result up to the next whole unit.
What if my contribution margin is negative?
There is no break-even point: each sale increases the loss. In our second scenario, a $12.99 price against $13.50 of direct costs plus fees lost $2.49 per unit. Raise the price, reduce per-unit costs, or reduce ad cost per sale until contribution is positive; only then does a break-even volume exist.
Does break-even include my salary and rent?
They belong in fixed costs if they must be paid regardless of sales volume — many small sellers understate fixed costs by leaving their own time out entirely, which produces a break-even point that is technically correct and practically misleading. Include what the business truly must cover.
References
- OpenStax, Principles of Managerial Accounting — "Calculate a Break-Even Point in Units and Dollars" — https://openstax.org/books/principles-managerial-accounting/pages/3-2-calculate-a-break-even-point-in-units-and-dollars — Accessed 24 October 2026.
- OpenStax, Principles of Managerial Accounting — "Explain Contribution Margin and Calculate Contribution Margin Per Unit, Contribution Margin Ratio, and Total Contribution Margin" — https://openstax.org/books/principles-managerial-accounting/pages/3-1-explain-contribution-margin-and-calculate-contribution-margin-per-unit-contribution-margin-ratio-and-total-contribution-margin — Accessed 24 October 2026.
- U.S. Small Business Administration, Calculate your startup costs — https://www.sba.gov/business-guide/plan-your-business/calculate-your-startup-costs — Accessed 24 October 2026.
Related reading: UTM Campaign Builder.