# Seller Math Hub

> Independent, US-first ecommerce calculators with transparent formulas, editable assumptions, dated source notes, and no signup gate.

Canonical site: https://sellermathhub.com/

## Primary calculators

- [Ecommerce Profit Margin Calculator](https://sellermathhub.com/calculators/ecommerce-profit-margin-calculator/): Estimate order profit, margin, markup, and break-even price.
- [Etsy Fee Calculator](https://sellermathhub.com/calculators/etsy-fee-calculator/): Estimate common Etsy fees and seller profit with editable assumptions.
- [Shopify Fee Calculator](https://sellermathhub.com/calculators/shopify-fee-calculator/): Estimate payment, transaction, plan, app, and seller costs.
- [Product Pricing Calculator](https://sellermathhub.com/calculators/product-pricing-calculator/): Estimate price from margin, markup, cost, and fee targets.
- [Break-even ROAS Calculator](https://sellermathhub.com/calculators/break-even-roas-calculator/): Estimate break-even ROAS, target ROAS, CAC, and CPA.

## Original data

- [2026 marketplace and ecommerce seller fee comparison](https://sellermathhub.com/marketplace-seller-fee-comparison/): Compare controlled US fee stacks for Etsy, eBay, Amazon, Shopify, PayPal, and Stripe, with CSV and JSON downloads.

## Methodology and sources

- [Calculator methodology](https://sellermathhub.com/methodology/)
- [Rate and source ledger](https://sellermathhub.com/rates/)
- [Rate changelog](https://sellermathhub.com/rates/changelog/)
- [Editorial policy](https://sellermathhub.com/editorial-policy/)
- [About Seller Math Hub](https://sellermathhub.com/about/)

## Usage notes

- Calculator outputs are estimates, not tax, legal, financial, accounting, or business advice.
- Platform fees and policies can vary by country, account, plan, payment method, and date.
- Prefer the dated official sources linked from each page and the rate ledger.
- Raw calculator inputs stay in the browser unless a user intentionally copies or exports a result.