Rental Property Cash Flow Calculator
Estimate rental property cash flow after vacancy, operating costs, reserves, and financing, with return targets and downside tests.| Metric | Current estimate | Planning note | Copy |
|---|---|---|---|
| {{ row.label }} | {{ row.value }} | {{ row.note }} |
| Line item | Monthly | Annual | Treatment | Copy |
|---|---|---|---|---|
| {{ row.label }} | {{ row.monthly }} | {{ row.annual }} | {{ row.note }} |
| Scenario | Cash flow | DSCR | Cash-on-cash | Signal | Copy |
|---|---|---|---|---|---|
| {{ row.label }} | {{ row.cashFlow }} | {{ row.dscr }} | {{ row.cashOnCash }} | {{ row.signal }} |
| Target | Required rent | Meaning | Copy |
|---|---|---|---|
| {{ row.label }} | {{ row.requiredRent }} | {{ row.note }} |
Introduction
Monthly rent is not monthly profit. A rental property must absorb vacancy and collection loss, recurring operating costs, repair and replacement reserves, and financing before it produces cash for the owner. Cash-flow underwriting organizes those assumptions into a consistent pre-tax estimate so weak income or an omitted cost is easier to spot.
Net operating income, or NOI, measures property income after vacancy and operating expenses but before loan payments. This separation matters because the same building can have the same NOI under two different financing plans. Debt service is then subtracted to reach pre-tax cash flow.
- Cap rate compares annual NOI with purchase price and does not depend on the chosen loan.
- Debt service coverage ratio (DSCR) compares NOI with principal-and-interest debt service.
- Cash-on-cash return compares annual pre-tax cash flow with acquisition cash such as down payment, closing costs, initial repairs, and reserves.
- Break-even occupancy estimates the share of scheduled income needed to cover modeled operating costs and debt service.
A positive base-case result is only a starting point. Rent evidence can be wrong, taxes and insurance can reset, repairs arrive unevenly, and financing terms can change before closing. Downside scenarios reveal how quickly the cushion disappears when rent falls, vacancy rises, costs increase, or the interest rate is higher.
The estimate remains narrower than a full investment analysis. It excludes depreciation, income tax, appreciation, sale proceeds, adjustable-rate behavior, mortgage insurance, and many lender-specific adjustments. Local law, lease terms, property condition, insurance coverage, and tax treatment still require separate review.
How to Use This Tool:
Build the property economics first, then add financing, acquisition cash, and downside assumptions.
- Choose a deal profile for an example or use Custom. Keep every entered amount in one currency; the Currency symbol changes labels but performs no exchange-rate conversion.
- Enter purchase price, supported monthly rent, vacancy allowance, and recurring costs. Include owner-paid utilities and other operating expenses in Advanced when they apply.
- Add down payment, fixed annual interest rate, and amortization term. Use a zero-year term only for a 100% down-payment scenario.
- Record closing costs, initial repairs, and acquisition reserves because they change cash invested and cash-on-cash return even though they do not reduce NOI.
- Set only defensible return targets and stress assumptions, then compare the deal snapshot with the underwriting ledger, combined downside, and required rents.
Interpreting Results:
Begin with monthly cash flow and trace it back through NOI and debt service. A positive number means the modeled monthly income covers the entered vacancy, operating expenses, reserves, and principal-and-interest payment. It does not mean the property will meet every real cash need.
DSCR is shown only when debt service exists. A value below 1.00 means NOI is insufficient to cover the modeled loan payment. An all-cash result has no applicable DSCR, so cap rate and cash-on-cash return carry more of the comparison.
Target rents are reverse calculations, not rent forecasts. Compare break-even, target-return, and combined-stress rents with current market evidence and legal constraints. If a required rent is unsupported, changing the target in the form does not improve the underlying deal.
- Subsidy risk means modeled monthly cash flow is below zero.
- Debt shortfall means cash flow is not negative but DSCR is below 1.00.
- Below target means core costs are covered while an enabled DSCR or cash-on-cash target is missed.
- Meets targets means the base case clears the entered screens, not that the investment is recommended.
Technical Details:
The underwriting chain starts with scheduled income, removes a vacancy allowance, subtracts property operating expenses to obtain NOI, and then subtracts level principal-and-interest debt service. Percent-based maintenance and capital-expenditure reserves are calculated from rent, while the management fee is calculated from effective gross income after vacancy.
Formula Core
The income and operating-cost equations define the property result before financing.
Operating expenses include monthly property tax and insurance, fixed dues, maintenance reserve, management fee, CapEx reserve, owner-paid utilities, and other recurring costs. Debt service is deliberately excluded from NOI.
A financed scenario uses the standard level-payment formula, with loan amount equal to purchase price minus down payment.
P is principal, r is the annual interest rate divided by 1,200, and n is the term in months. At a zero rate, payment is principal ÷ months. A 100% down payment or zero principal produces no debt service.
Cash invested equals down payment + closing costs + initial repairs + initial reserve. Break-even occupancy equals (operating expenses + debt service) ÷ gross scheduled income × 100. Full floating-point precision is retained; Money precision changes only display rounding.
Rule and Transformation Core
| Stage | Exact rule |
|---|---|
| Verdict order | Cash flow < 0 gives Subsidy risk; otherwise DSCR < 1 gives Debt shortfall; otherwise a result below an enabled target gives Below target; otherwise no debt gives Unlevered income; remaining cases give Meets targets. |
| Rent stress | Multiply base rent by 1 − rent reduction ÷ 100. |
| Vacancy stress | Add the entered percentage points to base vacancy, capped at 95%. |
| Expense stress | Multiply the complete modeled operating-expense total by 1 + expense increase ÷ 100. |
| Rate stress | Add the entered percentage points to the fixed loan rate and recalculate debt service. |
| Required rent | Search upward for the lowest base rent that reaches zero cash flow, the selected return threshold, or combined-stress break-even. |
Equality belongs to the passing side: zero cash flow is not Subsidy risk, DSCR exactly 1.00 is not Debt shortfall, and a return exactly equal to its enabled target is not Below target.
Responsible Use:
This educational pre-tax estimate is not financial, investment, legal, tax, lending, appraisal, or property-condition advice. Verify every assumption against leases, market rent evidence, tax bills, insurance quotes, inspection findings, reserve studies, lender documents, and local requirements.
- Model one currency consistently; no exchange-rate conversion is performed.
- Separate recurring operating expenses from acquisition cash and financing so NOI, cash flow, and cash-on-cash return are not distorted.
- Review excluded items such as depreciation, income tax, mortgage insurance, adjustable rates, balloon payments, appreciation, sale costs, and lender-specific DSCR adjustments.
References:
- Underwritten DSCR, Fannie Mae Multifamily Guide.
- How do mortgage lenders calculate monthly payments?, Consumer Financial Protection Bureau, reviewed December 11, 2024.
- Publication 527, Residential Rental Property, Internal Revenue Service, 2025.