Calculator methodology · Last reviewed August 5, 2026
How SellerMargin Tools estimates profit, fees, and landed cost
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.
We keep fee rates editable on purpose. A fixed hidden rate can become wrong when a marketplace updates category rules, a seller changes fulfillment method, or a product moves into a different category. The calculators are designed to show the formula and let you replace every important assumption.
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.
Source and update policy
SellerMargin Tools prioritizes official marketplace documentation, seller help centers, public fee pages, and official policy pages for fee references. When an exact account-specific fee cannot be known, the calculator uses editable planning defaults and labels the result as an estimate.
Amazon referral fee, FBA, Handmade, Etsy payment processing, Offsite Ads, Shopify payment fees, TikTok Shop commissions, and import duties can change by country, category, account, product dimension, fulfillment method, campaign, tax treatment, or date. For final pricing, settlement, tax, or customs decisions, always verify inside the relevant seller dashboard or with a qualified advisor.
When Search Console shows new fee-related search demand, we update the most relevant calculator page, guide, FAQ, spreadsheet template, or internal link cluster instead of changing every page at once.
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.