MarginMath

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Profit, pricing, marketplace fees, 2026 US tax deductions, student loans and benefits. Every tool is free, private and shows its working.

Seller pricing

Markup CalculatorEnter any two of cost, markup or price to get the third, plus profit and margin.Open calculator →
Profit Margin CalculatorGross profit, margin and markup, with totals for any quantity.Open calculator →
Margin ↔ Markup ConverterTurn a target margin into the markup you need, and back.Open calculator →
ACoS & TACoS CalculatorAd cost of sales, ROAS, TACoS and your break-even ACoS.Open calculator →

Marketplace fees

Etsy Fee CalculatorListing, transaction, processing and Offsite Ads fees.Open calculator →
eBay Fee CalculatorFinal value fees by category, plus per-order fee.Open calculator →
Amazon FBA CalculatorReferral and FBA fees from size and weight, with profit and ROI.Open calculator →
Amazon vs eBay vs EtsyOne product, three marketplaces: where you keep the most.Open calculator →
Whatnot Fee CalculatorCommission and processing on live sales, with break-even price.Open calculator →
TikTok Shop Fee CalculatorReferral fee, creator commission, shipping and returns.Open calculator →

2026 tax deductions (US)

Schedule 1-A CalculatorAll four new deductions and your total federal tax saved.Open calculator →
No Tax on OvertimeDeduction on the overtime premium, up to $12,500 ($25,000 joint).Open calculator →
No Tax on TipsUp to $25,000 of qualified tips, with the income phase-out.Open calculator →
$6,000 Senior DeductionExtra deduction for people 65+, $12,000 for couples.Open calculator →
Car Loan Interest DeductionUp to $10,000 of interest on a new US-assembled vehicle.Open calculator →

UK tax

Making Tax Digital CheckerDo you need MTD for Income Tax? Start date and quarterly deadlines.Open calculator →

Student loans & benefits

RAP Student Loan CalculatorNew Repayment Assistance Plan payment, payoff and forgiveness.Open calculator →
Medicaid Work Requirements Checker80-hour rule, income test and exemptions from 2027.Open calculator →

More free calculators

Built for online sellers and US workers. No sign-up, nothing leaves your browser.

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Free, no sign-upEvery calculator is free to use, with no account.

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Private by designYour numbers are worked out in your browser and never sent to us.

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Sources you can checkRates come from official fee pages and IRS guidance, linked on each page.

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Kept up to dateFees and tax figures checked November 2026.