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About RentVsBuyMath

A free calculator with one job: give you the honest math.

Why this exists

"Should I buy or keep renting?" is one of the biggest financial decisions most people ever make — often a difference of hundreds of thousands over a few decades. Yet the tools available are surprisingly poor. The best-known calculator sits behind a newspaper paywall. Many free ones are built by parties with a stake in your answer — lenders, brokerages, listing sites — and most quietly skip the factors that decide the outcome: the opportunity cost of your down payment, selling costs, tax rules as they actually work, and what the cheaper party should be doing with the monthly difference.

RentVsBuyMath.com is our answer: a genuinely free calculator that counts everything, explains everything, and doesn't care which answer you get.

What makes it different

  • Symmetric math. Whichever path is cheaper in a given year, that saver invests the difference. Most calculators only credit the renter — which quietly biases the result.
  • Everything on the table. Mortgage amortization, PMI with automatic cancellation, closing and selling costs, property tax growth, maintenance, insurance, rent inflation, investment fees, capital gains tax, and the U.S. home-sale exclusion.
  • Documented formulas. The full model is public on the methodology page — every formula, every default, every source. If you find an error, tell us and we'll fix it.
  • Honest about uncertainty. The verdict comes with a sensitivity check showing which assumptions could flip it.
  • No paywall, no signup, no data collection. Calculations run in your browser.

Who's behind it

RentVsBuyMath was built by Jonathan Nyst, a fintech growth professional, as an independent project. It has no affiliation with any lender, brokerage, or real-estate platform. The site is supported by advertising, which never influences the math: the calculator's output depends only on your inputs.

Open methodology, open source

The calculation engine is open source under the MIT license and covered by an automated test suite. Corrections and suggestions are welcome — reach us via the contact page.