How the rental math works
Gross rent is the monthly rent times 12. Vacancy comes off that gross figure. What remains is effective income. Operating costs are annual taxes, annual insurance, monthly HOA times 12, and the monthly reserve times 12. Net operating income is effective income minus those costs. The loan payment is not an operating cost.
DSCR is NOI divided by the annual payment. An amortizing payment uses the standard mortgage formula. An interest-only payment is the balance times the rate, divided by 12. Monthly cash flow is NOI minus the annual payment, divided by 12.
Cash invested is the purchase price plus buying costs minus the loan. Cash-on-cash is the annual cash flow divided by that cash. Cap rate is NOI divided by the purchase price, so it ignores the loan on purpose.
How to read a result
A DSCR under 1.00 means the NOI does not cover the payment. Between 1.00 and 1.25, the payment is covered with a thin cushion. Many screening sheets look for something around 1.25. That threshold is a habit in the industry, not a quote and not a promise that a loan exists at the rate you typed.
If cash-on-cash is blank, the loan is large enough that none of your cash remains. Cash flow can still be positive. Cap rate will not move when you change the rate or the term, because the loan is not in it.
This page leaves out income tax. Put property management and repairs in the monthly reserve or they will not be counted. For a refinance after rehab, use the BRRRR calculator. For a sale, use the flip calculator.