Rental cash flow calculator

Income is not the same as rental cash flow

The rent a listing advertises is the largest number in this calculation and the least useful one on its own. Vacancy, management, repairs, reserves, taxes, insurance, and the mortgage payment all take a share before anything is left over — and it is common for a property with healthy-looking rent to still lose money every month once debt service is included.

Who should use this calculator

Use it once you have a specific rental property with a real or realistic rent figure, and you want to know what it would actually put in your pocket each month after financing — not just whether the rent "sounds like enough." It is the natural next step after screening a property with the Cap Rate Calculator, which deliberately leaves financing out.

What each input means

• Monthly rent and other income — scheduled rent plus any additional income such as parking or laundry, before any loss.
• Vacancy/collection loss — the percentage of scheduled income you expect to lose to vacancy and uncollected rent over a year.
• Annual property tax and insurance — the property's fixed annual carrying costs.
• Monthly HOA and owner-paid utilities — recurring costs the owner pays directly, separate from what a tenant pays.
• Management, repairs reserve, and capital reserve — each entered as a percentage of effective income, covering property management, routine repairs, and larger future replacements.
• Monthly debt service — the mortgage principal-and-interest payment on this property.

How the calculation works

The calculator begins with scheduled rent and other income, subtracts the vacancy or collection-loss assumption, and produces effective income. It then subtracts property tax, insurance, HOA, owner-paid utilities, management, repair reserve, and capital reserve to calculate net operating income (NOI). Debt service is subtracted afterward to show pre-tax cash flow.

Keeping debt service outside operating expenses matters: net operating income describes property operations before financing, while cash flow reflects the selected financing. Two investors can therefore have the same NOI but different cash flow because their loans differ.

A worked example, using the figures already loaded above

At the default $3,000 monthly rent, annual gross scheduled income is $36,000. A 5% vacancy assumption removes $1,800, leaving $34,200 of effective income. Management (8%), repairs (5%), and capital reserve (5%) of that effective income come to $2,736, $1,710, and $1,710. Added to $6,000 of property tax and $1,800 of insurance, total operating costs are $13,956, leaving NOI of $20,244. Subtracting the default $1,800 monthly ($21,600 annual) debt service leaves a pre-tax cash flow of about −$1,356 a year, or about −$113 a month — this example, using the page's own default numbers, actually loses a small amount of cash every month once financing is included, even though the NOI on its own looks reasonable.

How to interpret the result

A positive NOI with a negative cash flow, as in the example above, means the property covers its own operating costs but not the loan used to buy it — the fix is usually a larger down payment, a lower price, a lower rate, or higher rent, not a smaller repairs or vacancy assumption. Compare the monthly cash flow against your own tolerance for a property that requires you to contribute cash some months, and revisit each percentage assumption individually rather than treating the final number as fixed.

What this calculator does not include

• Income tax, depreciation, or any tax-related benefit or liability of owning the property.
• Acquisition costs, closing costs, or costs of eventually selling the property.
• Unscheduled or unusually large repairs beyond the reserve percentages you set.
• Appreciation or any change in the property's value over time.

Why the result is an estimate

Every figure is arithmetic on the percentages and dollar amounts you entered; none of it is fetched from a listing, lender, or tax authority. Actual vacancy, repair costs, and management fees vary by market and property, so the further your inputs are from the real numbers, the further this result will be from what the property actually produces.

Common mistakes to avoid

• Vacancy and collection loss, even when the unit is currently occupied — every unit is vacant sometimes.
• Management cost, including a value for management work when appropriate, even if you plan to self-manage at first.
• Recurring repairs and larger capital replacements, not just this year's rent check.
• Taxes, insurance, HOA, utilities, licensing, and other property expenses that a rent listing never mentions.

Related guides and calculators

• Cap Rate calculator — an unlevered screening ratio to use before financing is decided.
• Rental cash-flow basics guide — the full cash-flow bridge from advertised rent to owner cash flow.
• Sell or Rent calculator — compare renting this property out against selling it now.