DealMath: Rental Property Calculator

Grade any listing A-F, find your max offer price, stress-test rates, build rehab costs and track your portfolio. Auto-filled.

DealMath is a rental property calculator and deal analyzer for real estate investors. Open any listing on Zillow, Redfin or Realtor.com and instantly see the cap rate, cash-on-cash return, monthly cash flow, DSCR and an A–F deal grade, auto-filled from the page. Decide in seconds whether a house is a good rental investment, before you build a spreadsheet. FREE (no account, no sign-up) • Deal grade A to F against your own investing targets, with the reason it isn’t higher • Red-flag warnings: rent that doesn’t cover the mortgage, thin DSCR, rent under the 1% rule, high property taxes, heavy HOA, high break-even occupancy • Expense reality check: flags insurance, maintenance, CapEx, vacancy and property-management numbers that are too optimistic • Price, taxes, HOA and rent estimate read from the listing; anything missing is estimated and clearly marked • Cap rate, cash-on-cash, DSCR, cash flow, principal paydown, gross rent multiplier, break-even occupancy • Offer-ceiling range: roughly the most you can pay and still hit your goal • Save 3 deals with a status (Watching, Visiting, Offered, Owned, Passed) and a note • Everything runs on your device PRO: for serious buy-and-hold investors • Max offer price: the highest price that still meets your cash flow, cash-on-cash or cap rate goal • Negotiation ladder: the deal at 5–20% off, graded, plus a down-payment comparison • Price-vs-interest-rate grid for mortgage rate stress tests • Rehab and closing-cost builder with all-in cost against after-repair value (ARV) • BRRRR calculator: cash left in the deal after the refinance • House hack and multi-unit analysis (owner-occupied units removed) • 30-year projection: equity, loan balance, cash flow, total return • FHA, seller financing, interest-only and points • Portfolio view: cash flow, cash invested and combined DSCR across your rentals • Ranked comparison of saved deals, unlimited saves, CSV export • Rent memory by ZIP and bedrooms, price-drop tracking • Printable one-page deal summary and shareable image card Estimates only; not financial advice. Verify taxes, insurance and rent before making an offer. DealMath is an independent tool. It is not affiliated with, endorsed by or sponsored by Zillow, Redfin or Realtor.com; those names belong to their owners and are used only to describe where DealMath works.