Order profit model
The Amazon, Etsy, and Shopify models combine item price and buyer-paid shipping as order revenue. The TikTok Shop US model currently uses item price alone. Monetary inputs are constrained to non-negative values, and rates are constrained to their valid ranges.
Fixed unit costs include product, fulfillment, storage, inbound placement, actual shipping, packaging, advertising, and other allocations. Variable costs scale with revenue. When a minimum platform fee applies, the model uses the greater of the percentage result and the minimum.
- Order revenue
R = item price + buyer-paid shippingTikTok Shop US currently uses R = item price.
- Platform fee
platform fee = max(R × platform rate, minimum platform fee)Models without a minimum set the minimum fee to zero.
- Payment fee
payment fee = R × payment rate + fixed payment fee- Expected return loss
return loss = R × planning return rateThis simplified expectation does not model recovered inventory, tax reversals, or per-order refund rules.
- Net profit and margin
net profit = R − all fees and costs; net margin = net profit ÷ R- ROI
ROI = net profit ÷ total cost
Break-even and target prices
Without a minimum-fee tier, the calculators solve price from fixed unit costs and the combined variable rate. Models such as Amazon first test the minimum-referral-fee region, then use the percentage-fee region. Buyer-paid shipping is subtracted from the solved order revenue.
If the combined variable rate and target margin reach or exceed 100%, the denominator is not positive. The model returns no finite target price instead of showing a misleading amount.
- Break-even item price
fixed unit costs ÷ (1 − combined variable rate) − buyer-paid shipping- Target item price
fixed unit costs ÷ (1 − combined variable rate − target margin) − buyer-paid shipping
Currency and payment comparison
The TikTok Shop US tool defines the exchange rate as purchase-currency units per one sales-currency unit. When the currencies differ, product cost in the sales currency equals purchase-currency cost divided by the exchange rate. A non-positive or invalid rate falls back to one and produces a risk warning.
The PayPal and Stripe tool applies an editable percentage and fixed fee for each provider. Currency conversion, disputes, refunds, international cards, in-person transactions, and negotiated pricing are excluded unless the user incorporates them into the assumptions.
- Fee per payment
transaction amount × percentage rate + fixed fee- Effective rate
fee per payment ÷ transaction amount- Monthly fees
unrounded fee per payment × monthly transactions
Rounding and display
Money outputs are rounded to two decimal places after calculation; ratios remain unrounded for display formatting. Monthly payment fees multiply the unrounded per-transaction fee before rounding, so they can differ by a few cents from the displayed per-transaction fee multiplied by volume.
Source review and change control
Default fees prioritize pricing, fee-policy, help-center, or seller-education pages controlled by the marketplace or payment provider. Third-party blogs, search snippets, and affiliate content may help discover a change but are not the final authority for a default rate.
Each fee record stores the applicable market, model assumption, official source, and last verification date. A date means the source and site default received a recorded comparison at that time. It does not guarantee that the provider made no later change or that every account, category, or transaction type uses the rate.
The site has no real-time fee API or automatic change alert. Reviews are triggered by official announcements, credible correction signals, or scheduled content maintenance. A default-rate change should update its explanation, verification date, and calculation tests together.
Model boundaries
The models generally do not calculate sales tax, VAT, income tax, duties, foreign-exchange spread, working-capital cost, tiered fees, promotional subsidies, disputes, refund administration fees, recoverable inventory value, or statement adjustments automatically. Only inputs shown in the interface enter the result.
Risk warnings use simple thresholds. They prompt an input review and are not a risk score or operating conclusion. Reconcile every result with provider dashboards, contracts, carrier bills, supplier invoices, settlement reports, and appropriate professional advice.