About RotoCurve
RotoCurve is a free calculator library for everyday decision math. The site focuses on seller profit, marketplace fees, shipping costs, savings, taxes, margins, ROI, and small business planning.
The goal is simple: make the hidden math visible before someone lists an item, accepts an offer, buys inventory, ships an order, chooses a platform, or compares a discount.
What RotoCurve publishes
- Interactive calculators that run in the browser.
- Seller guides that explain common profit and pricing decisions.
- Marketplace, shipping, and savings pages with clear assumptions and editable inputs.
- Plain-language notes about limitations, changing fees, and when users should verify details.
Important limitations
RotoCurve is for planning estimates. It is not financial, tax, legal, accounting, shipping, or marketplace advice. Fees, tax rules, carrier rules, platform policies, and regional details change. Users should verify critical decisions with official sources or qualified professionals.
Quality and usage notes
This page is intended to help users make clearer planning decisions with transparent assumptions. Results are estimates and should be checked against official sources when money, taxes, shipping, or marketplace rules are involved.
How to use this page well
Use this page as a planning aid, not a final quote or official rule. Replace defaults with your own numbers, compare more than one scenario, and check any important fee, tax, carrier, or marketplace policy against the official source before acting.
- Use real costs instead of rounded guesses whenever possible.
- Review the result together with shipping, returns, discounts, taxes, and payment fees.
- Save or repeat the calculation when costs change, because small inputs can change profit quickly.