Rental property calculator
Get cap rate, cash flow, and cash-on-cash return on any rental in seconds — with real per-state property tax and insurance, not a national average that quietly breaks the verdict in high-tax states. Honest, deterministic math. No signup.
Fixed assumptions: 8% vacancy, 10% maintenance, 10% management. Property tax + insurance are per-state estimates, not a county assessment or insurance quote.
- Mortgage (P&I)$1,958/mo
- Operating expenses$1,447/mo
- Cash invested (down payment)$70,000
- Gross rent multiplier13.3
Estimates only — verify rent comps, taxes and condition before making an offer. This is not financial advice or an appraisal.
Screening a lot of listings?
The Mortar Chrome extension runs this exact analysis automatically on any Zillow listing — no typing. Free to start.
How to read these numbers
Cap rate is the property's annual net operating income divided by its price, ignoring financing. It's the cleanest way to compare two properties on equal footing because it strips out your particular loan.
Cash-on-cash return is your annual pre-tax cash flow divided by the cash you put in (here, the down payment). It answers "what is my actual return on the money I invested?" and changes with your down payment and interest rate.
Monthly cash flow is what lands in your pocket after the mortgage and every operating expense — property tax, insurance, plus reserves for vacancy (8%), maintenance (10%) and management (10%). A deal that looks great on price can still bleed every month once real local taxes are in.
Frequently asked questions
How do you calculate cap rate on a rental property?
Cap rate is annual net operating income (rent minus operating expenses, before mortgage) divided by the purchase price. This calculator computes it deterministically from your inputs plus real per-state property tax and insurance, then shows the result as a percentage.
What is a good cap rate or cash-on-cash return?
It depends on your market and strategy, but many buy-and-hold investors look for a cap rate above 7% and cash-on-cash above 8% with positive monthly cash flow. This tool flags those thresholds as a starting point, not a recommendation — always verify against local comps.
Why does the state matter for a rental analysis?
Property tax and insurance vary enormously by state. A flat national average (around 1.2% tax) makes deals in high-tax states like Texas, Illinois and New Jersey look far better than they really are. This calculator uses real per-state rates so the verdict holds up where you actually buy.
Is this the same as the Mortar Chrome extension?
It uses the same deterministic math. The free calculator is for running numbers by hand; the Mortar Chrome extension does it automatically on any Zillow listing — it reads the price and details off the page and analyzes the deal in about ten seconds.
Are these numbers financial advice?
No. Every figure is an estimate to help you screen deals quickly. It is not financial, investment or real-estate advice, and it is not an appraisal. Verify rent comps, taxes and condition before making an offer.
Prefer the full write-up? Read the Mortar blog on analyzing rentals.