What Is a Mortgage Payment Calculator?
A mortgage payment calculator estimates your fixed monthly principal-and-interest (P&I) payment on an amortizing home loan. Given the loan amount, annual interest rate, and term in years, it returns the level monthly payment plus the total amount and total interest you will pay over the life of the loan. This tool covers the P&I portion only — property taxes, homeowners insurance, HOA dues, and PMI are billed separately and are not included.
How to Use It
Enter the amount you are borrowing (the loan principal, not the home price), the annual interest rate as a percentage (e.g. 6.5), and the loan term in years (commonly 15 or 30). The calculator converts the annual rate to a monthly rate and the term to a number of monthly payments, then computes your level monthly payment.
The Formula Explained
The standard amortization formula is $$M = P \times \frac{r(1+r)^n}{(1+r)^n - 1}$$ where P is the loan amount, r is the monthly interest rate (annual rate ÷ 12 ÷ 100), and n is the total number of monthly payments (years × 12). Each payment is identical; early payments are mostly interest while later payments are mostly principal. If the rate is 0%, the payment is simply \(P \div n\).
Worked Example
Borrow $300,000 at 6.5% for 30 years. The monthly rate is \(0.065 \div 12 \approx 0.0054167\), and \(n = 360\). Plugging into the formula gives a monthly payment of about $1,896.20. Over 360 payments that totals roughly $682,633, of which about $382,633 is interest.
FAQ
Does this include taxes and insurance? No. It shows principal and interest only. Add escrow items separately for a full PITI estimate.
What rate should I enter? Use your quoted annual percentage rate. The calculator divides it into a monthly rate automatically.
Can I model a 0% loan? Yes — enter 0 for the rate and the payment becomes the loan amount divided by the number of months.
