Calculator methodology
How SellerMargin Tools estimates profit
SellerMargin Tools is designed for quick planning before listing, sourcing, or scaling a product. The calculators use transparent, editable inputs instead of hidden fee tables because marketplace fees vary by country, category, account, product size, shipping method, and promotional program.
The result should be treated as an estimate. Before making pricing, sourcing, tax, or customs decisions, verify numbers in the relevant marketplace dashboard, official fee page, or with a qualified advisor.
Core formulas
Net profit = revenue - product cost - shipping cost - marketplace fees - payment fees - advertising cost - expected losses.
Profit margin = net profit / revenue.
ROI = net profit / product and inbound cost basis.
Landed cost = product cost + freight + insurance + duty + tax + customs or handling fees.
Reference sources
Amazon FBA
Amazon referral fees vary by category, and FBA fees vary by size tier, weight, destination, and program. The calculator keeps referral fee and FBA fee editable.
Etsy
Etsy listing, transaction, payment processing, offsite ads, currency conversion, and regulatory fees can all affect net profit. The calculator separates the major editable inputs.
Shopify
Shopify payment fees vary by plan, country, and provider. Store owners should include app and plan costs as a per-order allocation.
TikTok Shop
TikTok Shop fee schedules can vary by country, category, campaign, seller program, and policy update. The calculator treats platform and creator commissions as editable inputs.
Import duty and landed cost
Duty and tax depend on HS classification, declared value, destination country, shipping terms, and broker decisions. This calculator is for planning, not customs filing.