About the Rental Property Calculator
Before buying a property to rent out, investors work out whether the numbers make sense. This rental property calculator takes the price, the down payment and mortgage, the rent you expect, and the yearly costs of owning, and produces the figures investors compare: net operating income, cap rate, monthly cash flow after the mortgage, cash-on-cash return, debt service coverage ratio and gross rent multiplier. You can allow for empty months, repairs and property management as percentages of the rent, and add tax, insurance, HOA and other costs. It is designed to help compare properties quickly and test cautious cases.
Updated October 2026
How to use the Rental Property Calculator
- 1Enter the purchase price, down payment percentage, mortgage rate and loan term.
- 2Enter the closing and repair costs you will pay at purchase.
- 3Enter the monthly rent and the vacancy, repair and management percentages.
- 4Enter yearly property tax and insurance, and any monthly HOA or other costs.
- 5Read the cash flow, cap rate, cash-on-cash return and debt coverage.
A worked example
Take a 300,000 property rented at 2,500 a month with a 25 percent down payment. Yearly rent is 30,000. After 5 percent vacancy it is 28,500. Taxes and insurance are 4,800, repairs and management at 16 percent of rent are 4,560, so net operating income is about 19,140, a cap rate of 6.4 percent. The mortgage costs about 17,070 a year, leaving about 2,070 of cash flow, or around 173 a month. On 81,000 invested that is a cash-on-cash return of about 2.6 percent.
Stress-testing a deal
- Raise vacancy to 10 percent and see what happens.
- Increase repairs to 12 percent of rent.
- Try a mortgage rate one point higher.
- Lower the rent by 5 percent.
- Check that cash flow stays positive in a bad year.
Related tools
The Mortgage Calculator shows a precise loan payment, the ROI Calculator measures return on any investment, the Rent vs Buy Calculator compares owning a home with renting, the IRR Calculator handles uneven cash flows and the Payback Period Calculator shows how long it takes to recover your cash. Results are estimates, not investment advice.
Features
- Net operating income
- Cap rate
- Monthly and yearly cash flow
- Cash-on-cash return
- Debt service coverage ratio
- Gross rent multiplier and rent-to-price check
- Runs in your browser
Frequently asked questions
What is the cap rate?
The capitalisation rate is the net operating income for a year divided by the purchase price. It measures the return on the property if you bought it with cash, before any mortgage. A property with 19,000 of net income and a 300,000 price has a cap rate of about 6.3 percent.
What is net operating income?
It is the rent you collect after empty months, minus the costs of running the property: tax, insurance, repairs, management, HOA and other costs. It does not include mortgage payments or income tax. It is the number used to compare properties.
What is cash-on-cash return?
It is the yearly cash flow after the mortgage divided by the cash you put in, meaning the down payment and closing costs. It tells you the yearly return on your own money. A cash flow of 6,000 on 81,000 invested is a cash-on-cash return of about 7.4 percent.
What is a good debt service coverage ratio?
DSCR is the net operating income divided by the yearly mortgage payments. A value of 1.0 means the income exactly covers the loan. Lenders often want 1.2 or more to leave a safety margin. A value below 1 means the property does not cover its own mortgage.
What is the 1 percent rule?
A rule of thumb says monthly rent should be at least 1 percent of the purchase price for the property to cash flow. It is only a quick filter, and many markets do not meet it. The calculator shows the ratio for your numbers, but use cash flow and cap rate for decisions.
What should I assume for vacancy and repairs?
Many investors assume 5 to 8 percent of rent for empty periods and 5 to 10 percent for repairs and upkeep, rising for older buildings. If you use a manager, fees are often 8 to 10 percent of rent. Be cautious: underestimating costs is the most common mistake.