Real Estate & Investing
Multifamily Cash Flow Calculator
Combine unit rents, financing, and operating assumptions to see monthly cash flow, annual cash flow, and cash-on-cash return.
Calculation inputs
Enter the rent roll basics, loan terms, and operating assumptions.
Results
No result yet
Complete the fields and select Calculate to show results here.
About this calculator
This calculator projects monthly and annual cash flow for a multi-unit rental property once financing, vacancy, and operating costs are all accounted for. Investors and buyers use it to sanity-check whether a building will put cash in their pocket after the mortgage is paid.
How the calculation works
- Gross monthly income = number of units × average rent per unit
- Vacancy, maintenance, and management are percentages of gross monthly income
- Monthly debt service is a standard amortized payment on the financed balance
- Monthly cash flow = gross income − (vacancy + operating expenses + debt service)
- Cash-on-cash return = annual cash flow ÷ down payment × 100
Notes and assumptions
Percentage-based reserves are planning figures; actual maintenance varies with building age and systems.
Owner-paid utilities can swing cash flow significantly in older multifamily buildings.
How it works in plain English
The calculator starts with gross monthly income, which is the number of units multiplied by the average rent per unit. From there it subtracts a vacancy allowance, an estimate of maintenance and property management costs (each entered as a percentage of gross rent), monthly property taxes and insurance, and any utilities the owner covers rather than the tenants.
On the financing side, it converts your purchase price and down payment percentage into a loan amount, then calculates the standard amortized monthly payment from the interest rate and loan term. That payment is added to operating costs to get total monthly expenses.
Monthly cash flow is gross income minus total expenses, and annual cash flow is simply that figure times twelve. The tool also divides annual cash flow by the down payment to produce a cash-on-cash return, which shows the yield on the actual cash invested rather than on the full purchase price.
The formula
- Gross monthly income = units x average rent
- Total expenses = vacancy loss + maintenance + management + taxes/insurance + utilities + debt service
- Monthly cash flow = gross monthly income - total expenses
- Cash-on-cash return = (annual cash flow / down payment) x 100
Worked example
An 8-unit building averaging $1,250 rent per unit generates $10,000 in gross monthly income. At 5% vacancy that's a $500 loss, leaving $9,500 effective income. Maintenance at 8% and management at 6% of gross rent add up to $1,400, taxes and insurance run $1,500 a month combined, and owner-paid utilities are $450.
On a $980,000 purchase with 25% down ($245,000), the $735,000 loan at 6.75% over 30 years costs about $4,767 a month. Total expenses come to roughly $8,617, leaving monthly cash flow near $1,383, or about $16,600 a year — a cash-on-cash return of roughly 6.8%.
Frequently asked questions
Does the calculator include closing costs or renovation budgets?
No. Cash-on-cash return here is measured against the down payment alone. If you also spend money on closing costs, inspections, or rehab, add those amounts to your invested capital manually to see the true return on total cash out of pocket.
Why include vacancy loss if my units are currently full?
Vacancy loss models the turnover, non-payment, and re-leasing gaps that occur over time even in strong markets. Using a realistic vacancy percentage, rather than 0%, keeps the cash flow estimate from being overly optimistic during periods of full occupancy.
How is the monthly debt service calculated?
It uses the standard fixed-rate amortization formula based on the loan amount, annual interest rate, and loan term in months. It assumes a fully amortizing loan with no interest-only period, points, or prepayment adjustments, so if your actual loan includes those features, treat the payment shown here as an approximation rather than an exact figure from your lender.
What if maintenance and management costs vary by season or lease?
The calculator applies flat percentages of gross rent for simplicity, which works well for a stabilized annual estimate. For a property with irregular capital repairs or seasonal costs, treat the result as an average year rather than a forecast for any single month.
Can I use this for a single rental unit instead of a multifamily building?
Yes. Setting the number of units to 1 turns it into a single-property cash flow calculator using the same inputs and formulas, though a dedicated single-unit rental calculator may offer more relevant default assumptions and skip fields that only apply to buildings with several units, such as blended average rent across unit types.