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, in the log below.
How this site is made
Drafted with AI, computed by the engine, answered for by a person. The prose on this site is drafted with an AI model (Anthropic's Claude) working from the engine's output, then reviewed, edited and published under Jonathan Nyst's name; he is responsible for every page. Every dollar figure, threshold and verdict is computed by the open-source engine, not written, and an automated test suite checks that the copy still states what the engine currently computes - a figure that drifts fails the build. External facts (tax law, survey rates, market data) are taken from primary sources named on the page that uses them, with the date they were checked.
What the site does not do today. It carries no advertising, no affiliate links, no lead capture and no paid placements in the calculators comparison, and no page is generated in bulk. If any of that changes, the change is logged below on the day it happens. Rate-dependent copy is re-verified against the Freddie Mac survey monthly; when the numbers change, the page's date changes with them, and a page is re-dated only when its content changes, never for template or link housekeeping.
Corrections and updates
Substantive corrections and changes, newest first. Typos and wording are not logged; anything that changed a number, a claim or a date is.
- /best-rent-vs-buy-calculators
Rewrote the calculators page from a ranking that placed our own tool first into an unranked comparison; our tool now sits in a separate, disclosed section. The standalone NYT comparison page was merged into it and its old URL redirects here. A vendor scoring its own product is not useful to readers, and the two pages overlapped heavily.
- /numbers
Rebuilt as an open dataset: horizon-by-rate matrix, CSV and JSON downloads, citation block, data licence. The page listed figures without the assumptions, downloads and provenance a reader or journalist needs to reuse them.
- all guides and pages
Fixed the 'last updated' date shown on every page: it had been frozen at each page's publication date because the template read a field no page set. Dates now derive from the page's git history. A stale date under a changed page misleads readers about freshness.
- /best-rent-vs-buy-calculators and the former NYT comparison
Corrected the published test count, which two pages stated as 33 while the suite had grown to 127. The count now lives in one constant that every publishing page is tested against. Two pages contradicted the footer; the fix made the drift impossible to repeat, not just corrected once.
- /about
Removed a sentence saying the site was supported by advertising. It is not, and never has been. The claim was false.