How to Use This Mortgage Calculator
Enter the home price and your down payment — either as a dollar amount or a percentage; the two fields stay in sync automatically. Add the annual interest rate from your lender and select your loan term. Results update instantly as you type, showing your fixed monthly principal-and-interest payment, total amount paid over the life of the loan, and a year-by-year amortization breakdown.
Frequently Asked Questions
How is a mortgage monthly payment calculated?
The monthly payment uses the standard amortization formula: M = P × [r(1+r)^n] / [(1+r)^n − 1], where P is the loan amount (home price minus down payment), r is the monthly interest rate (annual rate ÷ 12), and n is the total number of payments (years × 12). Each payment covers accrued interest first, with the remainder reducing the principal balance, until the loan reaches zero at the final payment.
How much down payment do I need?
The required down payment depends on your loan type. Conventional loans typically require 3–20%. FHA loans allow as little as 3.5% with a 580+ credit score. VA and USDA loans can require no down payment for eligible borrowers. Putting down less than 20% on a conventional loan usually triggers private mortgage insurance (PMI), which increases your effective monthly cost. A larger down payment reduces both your loan amount and total interest paid.
What does this calculator not include?
This tool calculates your principal and interest (P&I) payment only. Your actual monthly housing expense will also include property taxes, homeowner's insurance, and — if your down payment is under 20% — PMI. Lenders often refer to the full payment as PITI (Principal, Interest, Taxes, Insurance). Ask your lender for a full Loan Estimate to see every cost component.
What is amortization?
Amortization is the process of repaying a loan through fixed, scheduled payments. Each payment covers the interest that has accrued since the last payment; the remainder reduces the outstanding principal. In the early years of a 30-year mortgage, most of each payment is interest — you may pay off surprisingly little principal in years 1–5. As the balance falls, the interest portion shrinks and principal paydown accelerates.
Should I choose a 15-year or 30-year mortgage?
A 30-year mortgage offers a lower monthly payment but costs far more in total interest. A 15-year mortgage means a higher monthly payment but dramatically less interest and faster equity growth. On a $400,000 loan at 7%, the 30-year option costs roughly $558,036 in interest over the life of the loan; the 15-year option costs about $247,158 — a difference of over $310,000. Use the calculator above to compare terms for your specific numbers.