Rental Property ROI & Cash Flow Calculator
Analyze a rental: monthly cash flow, cap rate, and cash-on-cash return from rent, expenses, and financing.
Published by Blueprint Dynamics. Planning tools, not professional advice. Read the formula, assumptions, and examples below before relying on a result. Independent professional review is not claimed. Learn more about our methodology →
AllTemplates • Blueprint Dynamics • hello@bpdynamics.io. Educational worksheet; entries and assumptions are not independently verified. This document is not tax, legal, medical, investment or engineering approval. Review current official rules and seek a qualified specialist where appropriate.
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No live prices, legal due diligence or return guarantees. Model financing, vacancy, tax, insurance and transaction costs separately; have an adviser review a real investment decision.
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About the Rental Property ROI & Cash Flow Calculator
Buying a rental property is really the purchase of a small business, and the price on the listing tells you almost nothing about whether that business will make money. What matters is the spread between what a tenant pays you and what the property costs you to own every single month. This calculator turns a candidate deal into the three numbers landlords actually underwrite on: monthly cash flow, capitalization rate, and cash-on-cash return.
The tool models the full stack of a leveraged purchase. You enter the purchase price, down payment percentage, interest rate, and loan term so it can amortize a real mortgage payment, then layer in monthly rent, a vacancy allowance, and a line-item list of operating expenses like property tax, insurance, maintenance, and property management. Because each of those levers moves the result, you can pressure-test a deal before you ever write an offer.
Cash flow is what keeps you solvent when a water heater fails, cap rate lets you compare properties of different sizes on equal footing, and cash-on-cash return tells you how hard the actual dollars you sank into the deal are working. Seeing all three together stops you from falling in love with a property that appraises well but bleeds cash.
How the Rental Property ROI & Cash Flow Calculator works
The engine first derives your down payment as purchase price times the down payment percentage, and the loan amount as the remainder. It then computes the monthly principal-and-interest payment with the standard amortization formula: payment = L * r * (1+r)^n / ((1+r)^n - 1), where L is the loan balance, r is the monthly rate (annual rate divided by 12), and n is the number of monthly payments (years times 12).
On the income side, effective rent equals monthly rent multiplied by (1 minus the vacancy percentage), which discounts your gross rent for the weeks a unit sits empty between tenants. Monthly cash flow is effective rent minus the sum of your operating expenses minus the mortgage payment. Note that property taxes and insurance here are entered as their own monthly lines rather than escrowed into the payment.
The return ratios use net operating income, defined as (effective rent minus operating expenses) times 12. Crucially, NOI excludes the mortgage, because a cap rate is meant to describe the property independent of financing: cap rate = NOI / purchase price. Cash-on-cash return divides annual cash flow (which does include the mortgage) by the actual cash you invested, calculated as down payment plus closing costs.
Worked example
Take the default deal: a $300,000 property with 20% down ($60,000), financed at 6.5% over 30 years. The loan of $240,000 amortizes to a monthly payment of $1,516.96. Rent is $2,400 with a 5% vacancy factor, giving effective rent of $2,280. Operating expenses total $742 per month ($300 tax, $100 insurance, $150 maintenance, $192 management).
Monthly cash flow works out to $2,280 - $742 - $1,516.96 = about $21 per month, or roughly $252 per year. Net operating income is ($2,280 - $742) x 12 = $18,456, so the cap rate is $18,456 / $300,000 = 6.2%. With $60,000 down plus $6,000 in closing costs, your cash invested is $66,000, making the cash-on-cash return $252 / $66,000 = about 0.4%.
That razor-thin cash flow is the lesson: a property with a respectable 6.2% cap rate can still barely cash flow once a 6.5% mortgage is bolted on, because your borrowing cost is nearly as high as the property's unlevered yield. Nudge rent to $2,600 or negotiate the price to $280,000 and the same screen swings to healthy positive territory.
Tips & common mistakes
- Do not skip the vacancy allowance to make a deal look better. Even in a hot market, budgeting 5% to 8% for turnover, cleaning, and re-listing is realistic; a property that only works at 0% vacancy is a property that does not work.
- Underwrite maintenance and capital reserves honestly. A common rule of thumb is 1% of property value per year for maintenance plus a separate CapEx reserve for big-ticket items like roofs and HVAC that the monthly maintenance line will not cover.
- Compare cap rate to local market cap rates, not to a fixed target. A 6% cap can be excellent in a low-risk metro and mediocre in a high-vacancy rural market; the cap rate only means something relative to comparable properties.
- Watch the relationship between your interest rate and cap rate. When your loan rate exceeds the cap rate you have negative leverage, meaning borrowing actually drags down your return, which is exactly what the tiny default cash-on-cash number is showing.
- If you use professional property management, keep that 8% to 10% of rent line in your expenses even if you plan to self-manage at first, so the deal still pencils out the day you hand it off.
Rental Property ROI & Cash Flow Calculator: frequently asked questions
What is the difference between cap rate and cash-on-cash return?
Cap rate measures the property's unlevered yield: net operating income divided by purchase price, ignoring your mortgage entirely. It lets you compare properties as if you paid all cash. Cash-on-cash return measures your leveraged result: annual cash flow after the mortgage, divided by the actual cash you put in (down payment plus closing costs). Cap rate describes the asset; cash-on-cash describes your specific financing of it.
Why is my cash flow so low even with a decent cap rate?
Because the mortgage is not part of the cap rate but is very much part of your cash flow. When your interest rate is close to or above your cap rate, most of the property's income goes straight to the lender. In the default example a 6.2% cap rate and a 6.5% loan leave almost nothing, which is a signal to renegotiate price, increase the down payment, or find a higher-rent property.
Should property taxes and insurance go in the expenses list?
Yes. This tool treats the mortgage line as principal and interest only, so you enter property tax, insurance, HOA, and any other carrying costs as separate monthly operating expenses. If your lender escrows taxes and insurance into a single payment, just split that escrow back out into these lines so the math is not double-counted.
What counts as cash invested for the cash-on-cash calculation?
The tool uses your down payment plus closing costs. In the real world you might also add initial repairs or make-ready costs to get a fuller picture, since those are dollars out of pocket before the property produces income. Adding them to the closing costs field will give you a more conservative and realistic cash-on-cash figure.
Does this account for appreciation and mortgage paydown?
No. This screen focuses on operating performance: cash flow, cap rate, and cash-on-cash return. It does not credit you for the equity you build as tenants pay down the loan, nor for potential appreciation or the tax benefits of depreciation. Those factors can make a low-cash-flow deal worthwhile over time, but they should be evaluated separately, not baked into the first-pass numbers.