Last updated: May 2026
Calculate monthly cash flow, cap rate, cash-on-cash return, and GRM for any rental property.
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Cash Flow = Effective Gross Income − All Operating Expenses − Mortgage Payment. Positive = profit, negative = you're covering the gap each month.
Cash-on-Cash Return = Annual Cash Flow ÷ Total Cash Invested. A 8%+ CoC is generally considered strong in most markets.
Cap Rate = Net Operating Income (before mortgage) ÷ Purchase Price. Used to compare properties independent of financing. Market cap rates typically range 4%–10%.
Gross Rent Multiplier (GRM) = Purchase Price ÷ Annual Gross Rent. Lower values indicate better value. Typical range: 6–12×.
50% Rule (quick estimate): Operating expenses on a rental typically run ~50% of gross rent. If expenses exceed this, scrutinize carefully.
⚠️ For planning purposes only. Does not include depreciation tax benefits, appreciation, or principal paydown. Actual results depend on local market conditions and property management quality.
Cash flow is the monthly amount left over after all property expenses are paid from rental income. It is the most fundamental metric in rental real estate because it determines whether a property feeds your bank account or drains it every month. Positive cash flow means the property runs itself financially; negative cash flow means you're subsidizing the property from your W-2 or other income. Many investors accept modest negative cash flow in high-appreciation markets, but this requires conviction in price growth that doesn't always materialize — a risk that becomes very visible when rents stagnate or a vacancy hits.
Cash flow is distinct from total return. A property with $0/month cash flow can still deliver excellent total returns if it appreciates, the mortgage is paid down, and tax benefits (depreciation) shelter other income. But cash flow is the only metric that tells you whether the property is operationally self-sustaining today. Sophisticated investors track cash flow alongside cash-on-cash return (annual cash flow ÷ total cash invested), cap rate (NOI ÷ property value), and gross rent multiplier (price ÷ annual gross rent) to build a complete picture of value.
| Metric | Poor | Average | Good | Great |
|---|---|---|---|---|
| Monthly cash flow per unit | <$0 | $0–$100 | $100–$300 | $300+ |
| Cash-on-cash return | <2% | 2–5% | 5–8% | 8%+ |
| Cap rate | <4% | 4–6% | 6–8% | 8%+ |
| Gross rent multiplier | >20× | 15–20× | 12–15× | <12× |
| Vacancy rate | >10% | 7–10% | 4–7% | <4% |
What is good cash flow for a rental property?
Most investors consider $100–$200/month per unit to be acceptable cash flow, with $300+/month per unit considered strong. Cash-on-cash return of 5–8% on invested capital is the more useful benchmark because it normalizes for purchase price and financing. In expensive coastal markets, many investors accept near-zero cash flow in exchange for appreciation; in Midwest or Sun Belt markets, 8–12% cash-on-cash is achievable with careful selection.
What is the difference between cash flow and ROI?
Cash flow is the net monthly (or annual) dollars in your pocket after all expenses. ROI (return on investment) is a broader metric that can include cash flow, equity paydown, appreciation, and tax benefits. A property might have low or zero cash flow but excellent total ROI due to rapid appreciation. Cash-on-cash return is the cash-flow-specific ROI: annual cash flow divided by total cash invested.
What is NOI in real estate?
Net Operating Income (NOI) is annual rental income minus all operating expenses, excluding mortgage debt service. NOI = Gross Rent − Vacancy Loss − Operating Expenses (taxes, insurance, maintenance, management, CapEx reserves). NOI is used to calculate cap rate and is the income figure a buyer or appraiser uses to value commercial and residential investment property independent of financing.
How do you calculate cap rate?
Cap rate = NOI ÷ Property Value (or purchase price). For example, a property with $18,000 annual NOI purchased for $300,000 has a cap rate of 6.0%. Cap rate measures the unlevered return on a property as if you paid all cash — it is financing-neutral and useful for comparing properties across different markets. A higher cap rate means higher yield but often also higher risk (older building, lower-demand area, etc.).
Does cash flow include mortgage paydown?
No. Cash flow calculations include the full mortgage payment (principal + interest) as an expense, so the principal paydown is already "spent" in the cash flow calculation even though it builds equity. Mortgage paydown is a separate component of total return that increases your net worth each month. To capture total economic return, investors add principal paydown to annual cash flow when calculating their comprehensive ROI.