About this calculator
One job: give you the honest math on renting versus buying, with nothing riding on which answer you get.
Jonathan Nyst Who is behind it
The author is the user. Jonathan Nyst is 40 and owns no property. Most of his friends and peers own one, some several — and for years the honest feeling was being behind. But "behind" assumes everyone started with the same chips, and nobody does: different countries, different incomes, different rents, different rates, different years to work with. The useful question was never why am I behind — it was what is the right move from where I actually stand, today. He couldn't find a tool that answered that question simply and exhaustively at the same time, so he built one.
Professionally, Jonathan spent fifteen years in banking, fintech, payments and data-driven marketing, at CMO and Head of Marketing level. That career is precisely why this site looks the way it does: he has seen from the inside how "free calculators" are built as lead-generation funnels — tuned to conclude that you should buy, because someone gets paid when you do. RentVsBuyMath is the calculator with no funnel. Nobody here earns anything from your answer.
What he is not: a lender, a broker, an agent, or a financial advisor — and this site is not financial advice. Where the model implements US tax rules, they come from primary sources, are encoded in the engine's automated tests, and are open for anyone to falsify — the methodology page documents every formula so you don't have to take anyone's word for it, including his.
Why it exists
"Should I buy or keep renting?" is one of the largest financial decisions most people make, and the tools for it are poor. The best-known calculator sits behind a newspaper paywall. Many free ones are published by parties with a stake in the answer, and most quietly skip the factors that actually decide it: the opportunity cost of the down payment, selling costs, tax rules as they really work, and what the cheaper party does with the monthly difference.
What makes the math different
Symmetric opportunity cost
- Whichever path is cheaper in a month, that side invests the difference
- Most calculators only ever credit the renter, which biases the result
- The renter's portfolio is taxed on its gains, so it is not a free ride either
Everything on the table
- Amortisation, PMI with automatic cancellation, closing and selling costs
- Property tax growth, maintenance, insurance, HOA, rent inflation, fund fees
- Standard versus itemised deductions, SALT cap, Section 121 exclusion
How to check it
The full model is public on the methodology page - every formula, every default and a plain statement of what it does not measure. The engine is MIT-licensed and covered by automated tests, including scenarios worked out by hand independently of the code, so a mistake in the implementation shows up as a failing test rather than a wrong answer on the page.
If you find an error, say so - corrections are made publicly.