Updated September 2026
Running a property through the calculator produces six or seven numbers at once, and it's easy to glance at them without really knowing which ones matter for which question. This page walks through each result in plain English — what it means, and roughly what a healthy range looks like.
The headline number: rent minus every monthly outflow, including the mortgage. It's the actual dollars left in your pocket (or the actual dollars you'd need to cover) each month. Positive cash flow means the property pays for itself and then some; negative cash flow means you'd be subsidizing it from other income every month, which some investors accept deliberately for a strongly appreciating property, but which should always be a conscious choice rather than a surprise.
Your annual cash flow divided by the actual cash you put into the deal (down payment plus closing costs plus upfront repairs), expressed as a percentage. This is the metric most directly comparable to "what would this money have earned somewhere else" — it's measuring return on the dollars you personally invested, financing included. There's no universal "good" number since it depends heavily on market and risk tolerance, but many buy-and-hold investors look for cash-on-cash return that's meaningfully above what a lower-risk alternative investment would return, to compensate for the extra work and risk of owning real property directly.
NOI divided by purchase price — the property's income relative to its price, with financing stripped out entirely. See the full cap rate limitations page for what this number is and isn't good for; in short, it's best used to compare properties against each other and against market norms, not as a stand-alone "good deal" signal.
Net Operating Income: annual rental income minus annual operating expenses, excluding the mortgage entirely. It's the property's own earning power, independent of how you (or anyone) financed it — the number cap rate is built from, and a useful figure on its own for comparing the operating performance of properties regardless of financing structure.
Principal and interest only, computed from the standard amortization formula — see mortgage math explained for the full formula and a worked example. It does not include property tax, insurance, or PMI, which are entered and shown separately in the expense breakdown.
Down payment plus closing costs plus upfront repairs — the actual out-of-pocket dollars the deal requires from you, and the denominator for cash-on-cash return. Two properties with identical price and financing terms can require very different total cash invested if one needs significant upfront repair work.
Grows rent and expenses by your chosen annual growth rate (3% by default) while holding the mortgage payment fixed, showing gross rent, total outflow, cash flow, and cumulative cash flow for each of the next five years. It's a simple straight-line model meant for directional planning — not a substitute for a full underwriting model that accounts for lease-up timing, capital expenditures, refinancing, or appreciation (a spreadsheet is a better tool for that level of detail — see calculator vs. spreadsheet). Watch the cumulative column specifically: it shows roughly how long it takes for accumulated cash flow to offset your total cash invested, a rough (not precise) payback-period read.
No single number here is "the answer" — cash flow tells you the immediate practical reality, cash-on-cash tells you the return on your specific investment, cap rate tells you how the property itself compares to others regardless of financing, and the projection gives a rough multi-year direction. A property can look strong on one metric and weak on another (a highly leveraged deal with strong cash-on-cash but thin absolute cash flow, for instance) — reading all of them together, alongside the itemized expense breakdown to see exactly where the money goes, gives a much more complete picture than any single figure.
Which number matters most? It depends on your goal — cash flow matters most if you need the property to be self-sustaining immediately; cash-on-cash matters most if you're comparing this investment against alternative uses of your capital; cap rate matters most if you're comparing this specific property against others regardless of how you'd finance it.
Why do I see "n/a" for cash-on-cash or cap rate? Cash-on-cash shows n/a if total cash invested is $0 (no down payment, closing costs, or repairs entered); cap rate shows n/a if purchase price is $0. Enter valid figures in those fields to see the calculated result.
Does a negative NOI mean the property is a bad investment? It means the property's operating expenses exceed its rental income even before financing — a serious warning sign in almost every case, since even an all-cash purchase would lose money monthly on operations alone.
This page is educational only, not investment advice. Verify all figures independently before making a purchase decision.