Methodology

Published calculators use fixed formulas that run in your browser from the numbers you enter. The same inputs produce the same outputs. Results are estimates for planning, not accounting, tax, or legal advice.

Percentages you type (such as a 2.9% payment fee or a 5% refund rate) are converted to the matching decimal form before they are used in the formulas. Currency symbols are for display; they do not change the math.

Each live tool states what it includes, what it leaves out, and which assumptions it uses. Where refunds or other uncertain events matter, the calculator uses an expected-value mix of successful and unsuccessful orders based on the rate and recovery assumptions you set. Change those assumptions if they do not match how your business actually works.

Platform-specific fee schedules are used only when a calculator includes them with a cited source and last-verified date. The E-commerce Profit Calculator does not publish those schedules; it applies a platform percentage only when you enter one. The Shopify Profit Calculator includes United States Basic, Grow, and Advanced online standard card rates and Shopify third-party transaction percentages from Shopify's official pricing documentation, with a last-verified date on that page. The Etsy Fee Calculator includes a United States Etsy Payments schedule (transaction fee, processing, listing allocation, regulatory operating fee, and Offsite Ads cap) from Etsy's official Help articles, with a last-verified date on that page. Additional Etsy countries are not auto-filled when that would require invented currency conversion. The TikTok Shop Fee Calculator includes United States 6% and 5% referral-fee presets from official TikTok Shop Seller University articles, with a last-verified date on that page. Creator commission is user-entered. Non-US TikTok Shop markets, FBT rate cards, and special collectible or pre-owned referral tiers are not auto-filled.

Outputs such as profit, margin, required selling price, break-even CPA, and break-even ROAS follow from your inputs and the disclosed model. The Break-Even ROAS Calculator and Product Pricing Calculator use user-entered payment and platform percentages only; they do not load marketplace or advertising-network fee tables. A required selling price is an economic threshold from those assumptions, not a claim that the market will pay it. Results are informational estimates. They are not a substitute for your books, tax filings, or professional advice.