Property Cash Flow Calculator
Estimate a rental's monthly and annual cash flow. Enter rent and other income, a vacancy allowance, each operating expense and your mortgage payment to see cash flow, NOI and optional cash-on-cash return.
Written by the CalcBundle Research & Editorial Team · Reviewed by the Quality Review Team · Transparent formulas · results are estimates, not advice. · Updated
Monthly cash flow
Enter your rent and expenses to calculate cash flow.
What a property cash flow calculator does
Cash flow is the heartbeat of a buy-and-hold rental. Appreciation is a bet on the future, but cash flow is what the property does for you every single month — and it is the difference between an asset that funds your life and a liability that drains it. A property cash flow calculator adds up all the money coming in, subtracts everything going out including the mortgage, and shows what remains monthly and annually. Done honestly, with every expense included, it is the most reliable test of whether a deal is worth doing.
How cash flow is built
- Effective income = (rent + other income) × (1 − vacancy)
- Operating expenses = tax + insurance + maintenance + management + HOA + utilities + other
- Cash flow = effective income − operating expenses − mortgage payment
- NOI (annual) = (effective income − operating expenses) × 12
Notice that the mortgage sits outside NOI and is subtracted only at the final step. That keeps two different ideas clear: NOI measures the property's earning power, while cash flow measures what lands in your account after financing.
Worked example
A single-family rental brings in $2,200 a month. Allow 5% for vacancy and effective income is about $2,090. Operating costs — $250 tax, $100 insurance, $150 maintenance and reserves, $175 management, and $60 for other items — total $735, leaving $1,355 before the mortgage. If the loan costs $1,150 a month, monthly cash flow is roughly $205, or about $2,460 a year. Small, but positive — and the calculator makes it obvious how a rent bump or a lower expense would move it.
The expenses people forget
Most cash flow disappointments come from optimistic expenses, not optimistic rent. A realistic analysis includes a vacancy allowance for the weeks between tenants, ongoing maintenance, capital reserves for the roof and mechanicals that will eventually fail, and management even if you self-manage today (your time has value, and you may not always want the job). Building those in up front is what separates a durable estimate from a hopeful one.
From cash flow to returns
Cash flow is the input to every return metric. Measure it against the cash you invested with the cash-on-cash return calculator, check the property covers its loan with the DSCR calculator, and add appreciation and sale proceeds for a full-hold return with the rental property ROI calculator.
Frequently asked questions
What is rental property cash flow?
Cash flow is the money left each month after collecting rent and paying all operating expenses and the mortgage. Positive cash flow means the property pays you; negative means it costs you out of pocket.
What expenses should I include?
Include property tax, insurance, maintenance, property management, HOA, utilities you cover, and any other recurring costs — plus your mortgage payment as debt service. A vacancy allowance makes the estimate more realistic.
Is the mortgage part of operating expenses?
No. Operating expenses and debt service are kept separate. NOI is calculated before the mortgage, and the mortgage is then subtracted to reach cash flow, so principal is not treated as a running cost.
How is cash-on-cash return calculated here?
If you enter the cash you invested, the calculator divides annual cash flow by that amount to show a cash-on-cash return alongside the monthly and annual cash flow — so you see both the dollars and the percentage in one place.
Why do so many new investors overestimate cash flow?
Because they count rent and the mortgage but forget the quiet costs in between. Leaving out a vacancy allowance, ongoing maintenance, capital reserves for big-ticket items, and management fees can turn a property that looks positive on a napkin into a negative one in reality. Including every recurring cost is the whole point of a proper cash flow calculation.
Should I budget for capital expenditures separately?
Yes. Routine maintenance keeps the property running, but roofs, HVAC systems and appliances eventually need replacing. Many investors set aside a monthly reserve (often 5–10% of rent) so a single large repair does not wipe out a year of cash flow. Fold that reserve into your expenses for an honest monthly figure.
Is negative cash flow always bad?
Not necessarily, but it is a risk. Some investors accept slightly negative cash flow in high-growth areas, betting on appreciation and loan paydown. The danger is that you must fund the shortfall every month regardless of what the market does, so negative cash flow should be a deliberate choice with cash reserves behind it, not an accident.
Related calculators
Cash-on-Cash Return
Measure annual pre-tax cash flow against the cash you actually invested.
Cap Rate
Compute capitalization rate from NOI and value, or solve for value or NOI.
Rental Property ROI
Estimate cash flow, cash-on-cash and total ROI for a financed rental, including sale.
DSCR
Work out debt service coverage ratio, or the debt supportable at a target DSCR.
Sources & methodology
- Formula
- Monthly Cash Flow = Gross Rent − Vacancy Loss − Operating Expenses − Mortgage Payment | Cash-on-Cash Return = Annual Cash Flow / Total Cash Invested × 100
- Reviewed
- September 2026
Primary sources
- BiggerPockets: Rental Property Cash Flow AnalysisIndustry-standard methodology for calculating rental property cash flow used by real estate investors.
- NOLO: Rental Property Expenses GuideLegal guide to deductible rental property expenses and net cash flow calculation.
Calculation methodology is documented on our methodology page. Reviewed by the CalcBundle Quality Review Team.
Disclaimer. This calculator provides estimates for informational purposes only. Results are based on the information you enter and the assumptions used by the calculator. Actual financial, tax, business valuation, lending, marketplace or investment outcomes may differ. Consider consulting a qualified professional for decisions involving significant amounts of money. Results are pre-tax estimates based on the figures you enter and do not account for income taxes or irregular capital expenses.