How do you calculate real estate cash flow?

True cash flow is calculated by taking your Gross Scheduled Income (Rent) and subtracting Vacancy, Operating Expenses (Taxes, Insurance, HOA, Maintenance, CapEx, Management), and your Mortgage Debt Service (P&I).

What is CapEx in real estate?

CapEx stands for Capital Expenditures. These are large, infrequent expenses that extend the life of the property, such as a new roof, a new HVAC system, or repaving a driveway. You must save a percentage of rent every month (usually 5-10%) to prepare for these inevitable costs.

What is the 50% Rule?

The 50% Rule is a quick screening tool used by investors. It assumes that total operating expenses (excluding the mortgage) will equal exactly 50% of the gross rent. If rent is $2,000, expect $1,000 in expenses.

Why should I include a management fee if I self-manage?

Your time is not free. If you don't factor in a management fee (usually 8-10%), you aren't calculating the return on your investment; you are calculating the return on your investment *plus* the wages of a part-time job.

Cash Flow Calculator

Stop guessing your rental profits. Accurately calculate your Net Operating Income (NOI) and true monthly cash flow by factoring in hidden expenses like CapEx reserves and vacancy rates.

Monthly Income

Gross Rent

Other Income

Fixed Expenses (Monthly)

Mortgage (P&I)

Taxes

Insurance

HOA / Fees

Variable Reserves (%)

Vacancy

Maintenance

CapEx

Property Mgmt

True Monthly Cash Flow

+$345/ mo

Your actual take-home profit after accounting for the mortgage, taxes, vacancy, and all maintenance reserves.

Net Operating Income (NOI)

$1,945

Income minus operating expenses (before mortgage).

Total Operating Expenses

$1,000

34.0% Operating Expense Ratio (OER).

The "Hidden" Expense Reserves

Vacancy Allocation (5%)-$155/mo

Maintenance Allocation (5%)-$147/mo

CapEx Allocation (5%)-$147/mo

Management Fee (8%)-$236/mo

Amateurs ignore these costs. Professionals hold this money in a separate bank account every month so they are prepared when the roof needs replacing or the tenant moves out.

How to Use the Cash Flow Calculator

Using our cash flow calculator is simple and requires no registration:

Enter the Gross Monthly Rent and any other income (like parking or laundry).
Enter your fixed monthly expenses: Mortgage (P&I), Taxes, Insurance, and HOA fees.
Set realistic percentages for your variable reserves. Standard safe estimates are 5% Vacancy, 5% Maintenance, 5% CapEx, and 8% Management.
The calculator will deduct all fixed and variable expenses to reveal your True Monthly Cash Flow and Net Operating Income (NOI).

Why Use a Cash Flow Calculator?

The number one reason new real estate investors go bankrupt is because they fail to accrue for CapEx and vacancy. This Cash Flow Calculator forces you to underwrite properties like a bank, ensuring you never buy a liability disguised as an asset.

How to Calculate Real Estate Cash Flow in 2026

Cash flow is the lifeblood of real estate investing. If a property does not produce positive cash flow, it is not an investment; it is a liability. Using a professional real estate cash flow calculator is the only way to ensure you are buying an asset that puts money into your pocket every single month.

The biggest mistake new investors make is calculating "cash flow" by simply subtracting the mortgage payment from the rent. This amateur mistake leads directly to bankruptcy because it ignores the massive, inevitable costs of maintaining a physical structure.

The 50% Rule of Thumb

Before doing a deep-dive analysis, professional investors use the "50% Rule" to quickly screen properties. This rule states that total operating expenses will roughly equal 50% of the gross rent (excluding the mortgage payment).

Example of the 50% Rule

If a property rents for $2,000 a month, expect your operating expenses (taxes, insurance, maintenance, management, vacancy) to cost roughly $1,000 a month.

This leaves you with an NOI (Net Operating Income) of $1,000. If your mortgage payment is $800, your true cash flow is $200 a month. If your mortgage payment is $1,200, the property will lose $200 a month.

The Four Hidden Reserves

To calculate accurate cash flow, you must accrue for expenses that haven't happened yet. Our rental property cash flow calculator forces you to input percentages for four specific reserves:

Vacancy (5-8%): You will eventually have to evict a tenant or wait a month to find a new one. Set aside 5% of your rent every month to cover the mortgage when the house is empty.
Maintenance (5-10%): Toilets clog and drywall gets dented. Assume 5% of rent goes to routine fixes.
CapEx (5-10%): Capital Expenditures are massive, infrequent repairs (like a new $10,000 roof or $5,000 HVAC). You must save for these every month, or they will bankrupt you when they inevitably break.
Property Management (8-10%): Even if you self-manage today, you should underwrite the deal assuming you pay a manager. Otherwise, you aren't building a scalable business.

NOI vs. True Cash Flow

It is critical to understand the difference between Net Operating Income (NOI) and Cash Flow. NOI is the income left over after paying all operating expenses, but before paying the mortgage. Cash Flow is what is left after paying the mortgage.

Commercial lenders base the value of a property entirely on its NOI. As an investor, you must ensure the NOI is high enough to comfortably cover your mortgage debt service while still leaving you with positive Cash Flow.