Rental Property Analysis: Key Numbers Every Investor Should Calculate

The five formulas that separate profitable rental investments from expensive mistakes — with real numbers.

Before you buy any rental property, you need to run the numbers. Not just the mortgage payment — all of them. Rental property analysis comes down to a handful of core formulas that each tell you something different about the investment. Together, they paint a complete picture of whether a property will generate positive cash flow, how much risk it carries, and whether it is priced right relative to comparable properties. This guide explains each formula, shows you how to calculate it with real numbers, and highlights what each metric can and cannot tell you.

1. Cap Rate (Capitalization Rate)

The cap rate is the most widely used metric for comparing rental properties across markets. It measures the property's income return as if you bought it all-cash — before financing.

Cap Rate = Net Operating Income (NOI) ÷ Purchase Price

NOI is the property's annual rental income minus all operating expenses — property taxes, insurance, management fees, maintenance reserves, vacancy allowance. NOI does not include mortgage payments or interest.

Example: You buy a rental house for $200,000. Annual rental income is $21,600 ($1,800/month). Annual operating expenses are $5,600 ($1,600 property tax + $1,200 insurance + $1,200 management + $1,600 maintenance reserve/vacancy).

NOI = $21,600 – $5,600 = $16,000

Cap Rate = $16,000 ÷ $200,000 = 8.0%

What this means: at 8% cap rate, the property generates 8% annual return on the purchase price before financing — a useful benchmark for comparing properties across markets. A higher cap rate means higher income return relative to price, but it can also signal higher risk or lower-quality tenant base in a tougher market. A lower cap rate in a strong market may be acceptable if appreciation prospects are strong or the area has strong tenant demand and low vacancy.

Use cap rate for: cross-market comparisons, initial screening, valuation based on income.

Don't use cap rate for: leveraged (financed) analysis, or to evaluate a property in isolation without comparing to alternatives.

2. Cash-on-Cash Return

Cash-on-cash return is the metric that actually matters once you introduce financing — because it measures the return on the actual cash you invested, not the purchase price.

Cash-on-Cash Return = Annual Cash Flow ÷ Total Cash Invested

Annual cash flow is the money left over after all operating expenses and mortgage payments. Total cash invested includes your down payment, closing costs, and any immediate repairs or improvements.

Example: Same $200,000 property, but this time you finance it. You put 20% down ($40,000) plus $6,000 in closing costs — total cash invested: $46,000. Your mortgage payment (PITI, 30-year at 7.0%) is approximately $1,018/month.

Annual cash flow = ($1,800 rent × 12) – ($5,600 operating + $12,216 mortgage) = $21,600 – $17,816 = $3,784/year

Cash-on-Cash Return = $3,784 ÷ $46,000 = 8.2%

Cash-on-cash return answers the question: "For every dollar I actually put in, what return am I getting?" A cash-on-cash return below your target threshold (commonly 6–10% for rental investors) means the deal needs either a lower purchase price, better financing terms, higher rents, or lower operating costs to work.

3. Debt Service Coverage Ratio (DSCR)

DSCR is the metric lenders use to decide whether to fund a rental property loan — and for good reason. It measures whether the property's NOI covers its mortgage payments, and by how much.

DSCR = Net Operating Income (NOI) ÷ Annual Debt Service

Annual debt service is the total of all principal and interest payments made on the loan in a year.

Example: Same property. NOI = $16,000. Annual mortgage payment = $12,216. DSCR = $16,000 ÷ $12,216 = 1.31x

What the numbers mean:

• DSCR of 1.0x: NOI just covers the mortgage — zero cushion
• DSCR below 1.0x: NOI does not cover the mortgage — negative cash flow
• DSCR of 1.2x: Standard conventional lender minimum; NOI covers mortgage with 20% cushion
• DSCR of 1.5x+: Strong coverage; lenders view this favorably; borrower has meaningful buffer

Most conventional lenders require a minimum DSCR of 1.2x. If your analysis shows DSCR near the minimum, stress-test it: what happens if vacancy rises 20%? If a major repair ($5,000 HVAC replacement) hits next month? A DSCR of 1.31x would drop to approximately 1.13x with a 15% vacancy spike — still technically above 1.0x but uncomfortably thin.

4. The 1% Rule vs. The 2% Rule (Gross Rent Multiplier)

The 1% and 2% rules are quick screening tools — not precise analysis methods. They help you quickly determine whether a property merits deeper analysis before running full numbers.

1% Rule: Monthly rent should be at least 1% of the total acquisition cost (purchase price + repairs + closing costs).

2% Rule: Monthly rent should be at least 2% of acquisition cost — an aggressive target found in high-growth or lower-price markets.

Example: $200,000 purchase + $10,000 repairs + $6,000 closing = $216,000 total acquisition cost. 1% rule target: $2,160/month minimum rent. 2% rule target: $4,320/month minimum rent.

Your property rents for $1,800/month. At 1% rule: $2,160 target vs. $1,800 actual = fails the 1% test. This is a signal to investigate further rather than walk away automatically. The property may still work if the market has strong appreciation prospects, if financing terms are unusually favorable, or if the 1% threshold is simply too high for the specific market. But it means the deal needs more scrutiny — not less.

Gross Rent Multiplier (GRM) is the inverse of the 1% rule expressed annually: GRM = Purchase Price ÷ Annual Rent. A GRM of 100 corresponds approximately to a 1% rule (because 12 months ÷ 12 = 1, or 100% ÷ 100 = 1%). The lower the GRM, the more attractive the property on a rent-to-price basis.

Example: $200,000 purchase ÷ ($1,800 × 12 = $21,600 annual rent) = 9.26 GRM

GRMs of 4–8 are generally considered favorable for residential rentals; GRMs above 10–12 often signal overpriced properties relative to rents, especially in softer markets.

5. Break-Even Occupancy Rate

Break-even occupancy tells you what percentage of units must be rented — at full market rent — to cover all expenses including the mortgage. It is the most important measure of downside risk.

Break-Even Occupancy = (Operating Expenses + Debt Service) ÷ (Gross Potential Rent)

Example: Same property. Operating expenses: $5,600. Debt service: $12,216. Total: $17,816. Gross potential rent at 100% occupancy: $21,600 (12 × $1,800).

Break-Even Occupancy = $17,816 ÷ $21,600 = 82.5%

Interpretation: the property must be occupied at full rent at least 83% of the time — every month — to avoid losing money. In a market with 95% average rental occupancy, this property has a comfortable 12.5-point buffer. In a market with 75% average occupancy, this property would lose money in most months.

Always compare break-even occupancy against local market occupancy rates. If your break-even is 82.5% but comparable properties in the area are achieving 95% occupancy, the deal works. If you are in a softer market with 70–75% occupancy, a break-even of 82.5% means the property will bleed cash most years.

Putting It All Together: The Full Picture

Conclusion

No single metric tells the whole story. A property that passes the 1% rule might have a terrible break-even occupancy in a soft market. A property with a strong cap rate might fail the DSCR if it is financed with expensive debt. Run all five metrics together and evaluate them as a set: cap rate for market comparison, cash-on-cash for return on your actual investment, DSCR for lender requirements, the 1% rule for quick screening, and break-even occupancy for downside risk. When all five tell a consistent story, you have a deal worth pursuing. When they conflict, the conflict itself tells you where the risk lies.

For more on the financing side of rental property investment, see our Landlord Essentials and Rental Property Tax Guide.