Rental cash flow calculator
Cash flow decides whether a rental feeds you or bleeds you every month. This free calculator subtracts the mortgage and every honest expense line, including real per-state property tax and insurance and reserves most quick tools skip. 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.
Every line in the cash flow formula
Cash flow = rent minus mortgage minus operating expenses. The mortgage is principal and interest on your down payment, rate and term. Operating expenses are property tax and insurance at real per-state rates, plus an 8% vacancy reserve, a 10% maintenance reserve and 10% management.
The two lines that quietly sink deals are local taxes and reserves. A property that cash-flows on a national-average tax assumption can lose money every month at the real local rate, and a deal that only works if nothing ever breaks is not a deal. If you want the full reasoning, the blog post on calculating rental cash flow walks through each line.
Frequently asked questions
How is rental cash flow calculated?
Monthly cash flow is rent minus the mortgage payment (principal and interest on your financing) minus every operating expense: real per-state property tax and insurance, an 8% vacancy reserve, a 10% maintenance reserve and 10% property management. What is left is the estimated amount the property pays you, or costs you, each month.
How much cash flow is good for a rental property?
There is no universal number, but many investors want at least $100 to $200 per month per unit after honest reserves. This tool's verdict requires positive cash flow to rate a deal worth pursuing. A deal that only works with zero vacancy and no maintenance budget is not really cash flowing.
Which expenses do people forget?
Local taxes and reserves. A flat 1.2% national tax assumption can be off by hundreds of dollars a month in Texas, Illinois or New Jersey, and skipping vacancy, maintenance and management reserves makes nearly any deal look profitable on paper. This calculator includes all of them by default.
Is negative cash flow always a deal breaker?
Not always, but you should know you are choosing it. Negative cash flow means you are paying monthly to hold the property and betting on appreciation or future rent growth. That is a strategy decision, not a screening error, as long as the numbers going in are honest.
Is this 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.
More free calculators
The full screen: cap rate, cash flow, cash-on-cash and a verdict, with real per-state taxes and insurance.
Net operating income over price, computed with real per-state property tax and insurance.
What the cash you actually put in earns, with your own down payment, rate and term.
Work backwards: the highest price at which a deal still clears your cash flow and return targets.
Prefer the full write-up? Read the Mortar blog on analyzing rentals.