Monthly payment, total interest, payoff date, and a full amortization schedule. Enter an extra payment to see exactly how much time and money you can save.
A mortgage is a loan secured against your home. When you buy a property, the lender pays the seller, and you repay the lender over a set term — typically 15 to 30 years — with interest. Each monthly payment covers the interest that has accrued on your outstanding balance plus a slice of the principal. In the early years, most of each payment goes to interest. As the balance falls, more of each payment erodes the principal. This progression is called amortization.
Four variables determine the size of your payment:
Making even a modest extra payment each month directly attacks your principal. Because future interest is calculated on the remaining balance, reducing the balance earlier creates a compounding benefit. On a $350,000 loan at 7% over 30 years, an extra $200/month eliminates roughly 5.5 years of payments and saves over $75,000 in interest. The larger the extra payment, the greater the effect. Use the extra payment field above to see your specific numbers.
This is one of the most common decisions buyers face. The 30-year mortgage is popular because its lower monthly payment gives more flexibility. But the price is substantial: you pay interest for twice as long. A $350,000 loan at 7% costs about $836,000 total over 30 years — nearly $490,000 in interest alone. The same loan over 15 years costs about $567,000 total, saving roughly $270,000. If you can manage the higher monthly payment, the 15-year option is usually the financially superior choice over the long term.
Private Mortgage Insurance protects the lender if you default. It is typically required when your down payment is below 20% of the purchase price. PMI usually adds 0.5%–1.5% of the loan amount per year to your costs, often rolled into the monthly payment. On a $320,000 loan, that is $133–$400 per month on top of principal and interest. PMI can be cancelled once your equity reaches 20%, either through loan paydown or rising home values. This calculator focuses on principal and interest; property taxes, insurance, HOA, and PMI are entered separately in lender quotes.
Every extra dollar in your down payment reduces the loan and therefore the monthly payment and total interest. It also improves your loan-to-value ratio (LTV), which lenders use to assess risk. An LTV below 80% typically unlocks better interest rates and eliminates the PMI requirement. Use the dollar/percent toggle above to model different down payment scenarios instantly.
The table below your results shows the progression of your loan year by year (or month by month). Notice how the principal column grows over time while the interest column shrinks — this is amortization in action. In the early years of a 30-year mortgage, roughly 75–80% of each payment goes to interest. By the final years, almost everything goes to principal. Understanding this helps you see why refinancing early in a loan is more impactful than refinancing late.