Rental Property Calculator — Cash Flow, Cap Rate & ROI

How to use the rental property calculator

1. Purchase and loan: enter the price, down payment percentage, interest rate, loan term and your closing and repair costs.
2. Income: enter the monthly rent, any other income such as parking or laundry, and a vacancy allowance (5% to 8% is common).
3. Expenses: property tax and insurance per year, HOA per month, maintenance as a percentage of rent, and management as a percentage of the rent you actually collect.

The results show your monthly cash flow, cap rate, cash-on-cash return, net operating income, mortgage payment, DSCR and whether the property passes the 1% rule — with a monthly breakdown.

Save, print or share your rental analysis

You don't have to start over next time. Under the calculator you can:

• Save the calculation in your browser with a name, then reopen it from "Saved calculations" whenever you like.
• Copy a link that reopens this exact calculation with all your numbers — on your phone, another computer or for someone you're planning with.
• Print a clean one-page report, or download it as a PDF. It shows your cash flow, cap rate, cash-on-cash return and a monthly income and expense breakdown, plus a QR code at the top: scan it with your phone camera and the calculation opens again with every number filled in.
• Download a CSV to open in Excel, Google Sheets or Numbers.

Nothing is uploaded: saved calculations stay on your device, and the link and QR code carry your inputs inside the address itself.

The key numbers explained

Net operating income (NOI) — yearly rent after vacancy minus operating expenses, before the mortgage. It shows what the property itself earns.

Cap rate — NOI ÷ purchase price. It lets you compare properties regardless of how they're financed.

Cash flow — what's left each month after the mortgage too. This is what actually lands in your account.

Cash-on-cash return — yearly cash flow ÷ the cash you invested (down payment + closing and repair costs).

DSCR — NOI ÷ yearly mortgage payments. Below 1.0 means the rent doesn't cover the loan.

1% rule — monthly rent ÷ price. A quick filter for whether a property is worth a closer look.

How the mortgage is calculated

The monthly principal and interest payment uses the standard amortization formula:

payment = loan × r ÷ (1 − (1 + r)^−n)

where r is the yearly rate ÷ 12 and n is the number of monthly payments. Property tax and insurance are listed separately as operating expenses.

Expenses new landlords forget

• Vacancy — even good units sit empty between tenants.
• Maintenance and capital expenses — roofs, water heaters and appliances wear out.
• Management — even if you self-manage now, pricing it in shows whether the deal still works if you hire help later.
• Turnover costs — cleaning, paint and listing fees between tenants.
• Rising tax and insurance — both tend to go up after a purchase.

Improving a deal that doesn't cash-flow

A larger down payment, a lower price, a lower interest rate or a realistic rent increase can each change the result. Try them in the calculator. If you're looking at it from the tenant side, the rent affordability calculator shows what renters in your area can comfortably pay. Our profit margin calculator is useful for side businesses such as furnished or short-term rentals.

Track what every unit really earns

Once you own the property, RentRoll, the VaultlyApps landlord dashboard, keeps the rent roll, expenses and maintenance requests in one private file and shows the real cash flow per unit and per year — ready for tax time. Open the free RentRoll demo with sample data.