Start with contribution profit, not sales revenue
The figure shown above is contribution profit after the variable costs you enter. It is not company net income. Subtract product cost, shipping and fulfillment, Shopify fees, Stripe processing fees and ad cost from the order's selling price. Divide the remainder by the selling price to see the modeled profit margin.
This per-order view is useful when a product sells well but a change in shipping, payment method or customer acquisition cost may be eroding the amount each sale contributes.
Enter only fees that apply to your payment setup
Shopify's additional transaction fee and a payment provider's processing fee are separate charges. A store using an external provider may pay both, while an order processed through Shopify Payments generally does not incur Shopify's third-party transaction fee. Set a fee line to zero when that charge does not apply; do not add a second processing rate just because both companies appear in the tool name.
Rates and fixed charges vary by plan, market and payment method. The defaults are examples, not a promise of what your store pays. Check the transaction details in your Shopify billing and payment-provider account before relying on a margin estimate.
The order-profit formula
Shopify fee = selling price × Shopify fee rate + Shopify fixed fee. Stripe fee = selling price × Stripe rate + Stripe fixed fee. Estimated contribution profit = selling price − product cost − shipping and fulfillment − Shopify fee − Stripe fee − ad cost per order. This calculator uses selling price as the fee base; your actual provider may use a different chargeable amount.
The maximum profitable CPA is the contribution remaining before ad cost. Break-even ROAS divides selling price by that pre-ad contribution. These two outputs describe the same acquisition limit in dollars and as a revenue-to-spend ratio.
A worked $68 order
Take the example shown in the calculator: $68 selling price, $18 product cost, $8 fulfillment, a 0.5% Shopify fee, a 2.9% Stripe fee plus $0.30, and $18.40 ad cost. The modeled fees are $0.34 and $2.27. After keeping unrounded values inside the calculation, contribution profit is $20.99 and the after-ad margin is 30.9%.
Before ads, the same order has about $39.39 available for acquisition. That gives a break-even ROAS of about 1.73x. Spending the entire $39.39 would leave no contribution for overhead or profit, so a business target should generally be more demanding than the break-even line.
Use CPA and ROAS as decision boundaries
Compare the maximum profitable CPA with your actual cost per acquired order, using the same revenue and attribution basis. If actual CPA rises above that ceiling, the modeled order loses money after ads. If it stays below, the difference is the contribution left under these assumptions.
A high ROAS does not fix an incorrect fee or shipping assumption. Recalculate when you change price, run a discount, move to another country or payment method, or switch fulfillment providers.
What this estimate leaves out
The calculator does not automatically include refunds, returns handling, sales tax or VAT, discounts, app subscriptions, payroll, rent, or customer support. It also does not model lifetime value or repeat orders. If those items matter to the decision, include the relevant per-order amount in your own planning model before calling a campaign profitable.
If customers pay a separate shipping charge, include that revenue consistently in your order value and check whether payment fees apply to it. The useful result is the one that matches how money actually flows through your checkout and payouts.