Introduction
A mortgage is a loan you take out to buy a home. You pay it back each month over many years, and the bank charges you interest on top of what you borrowed. Over time, that interest can add up to a lot of money — sometimes even more than the home price itself.
This mortgage interest calculator helps you see exactly how much interest you will pay over the life of your loan. Enter your loan amount, interest rate, and loan term to get a full breakdown of your costs. You can also add an extra monthly payment to see how much money and time you could save by paying down your loan faster. If you want a broader view of your full mortgage payment including taxes and insurance, try our mortgage calculator.
The calculator gives you a step-by-step solution showing the math behind your monthly payment. It also builds a complete amortization schedule so you can see how each payment splits between principal and interest, month by month. Use the built-in charts to visualize your balance over time, and compare up to three loan scenarios side by side to find the best option for your budget.
How to Use Our Mortgage Interest Calculator
Enter your loan details below to see how much interest you will pay, your monthly payment, and how extra payments can save you money and time.
Home Loan Amount: Type the total amount you plan to borrow in dollars. This is the price of the home minus your down payment. If you are still figuring out how much house you can afford, our home affordability calculator can help.
Annual Interest Rate: Enter the yearly interest rate on your mortgage. You can find this rate on your loan estimate or by asking your lender. Keep in mind that your rate differs from your APR, which includes additional fees and costs. Use our interest rate calculator to explore how different rates affect your payments.
Additional Monthly Payment: Type any extra money you want to pay each month toward your loan balance. This is optional. Enter 0 if you do not plan to pay extra. To dive deeper into prepayment strategies, see our mortgage extra payment calculator.
Loan Term: Pick how many years you have to repay the loan. Click a preset button like 15 or 30, or type in a custom number of years. If you are specifically comparing a 30-year mortgage to a shorter term, our dedicated tool can help with that comparison.
Loan Start Date: Choose the month and year your first mortgage payment begins. This helps the calculator show the exact date each payment is due.
After you fill in your details, the calculator will show your monthly payment, total interest paid, payoff date, and a full payment schedule. If you enter an extra monthly payment, it will also show how much interest and time you save. For a focused look at your payoff timeline, check out our mortgage payoff calculator.
What Is Mortgage Interest?
When you borrow money to buy a home, the bank charges you a fee for lending it to you. That fee is called mortgage interest. It is a percentage of the amount you still owe, and you pay it every month on top of paying back the money you borrowed. Unlike simple interest, mortgage interest is recalculated each month based on your remaining balance, which is why paying down principal early makes such a big difference.
The amount you borrow is called the principal. The percentage the bank charges you each year is called the interest rate. A higher rate means you pay more over time. A lower rate saves you money. Even a small change in rate — like half a percent — can add up to thousands of dollars over the life of a loan. If your current rate seems high, our refinance calculator can show you whether refinancing to a lower rate makes financial sense.
How Monthly Payments Work
Each monthly payment is split into two parts. One part goes toward the interest the bank charges you. The other part goes toward paying down your principal. Your full housing cost may also include property taxes, homeowners insurance, and private mortgage insurance — use our PITI calculator to see the complete picture. If your down payment is less than 20%, you may also owe PMI, which adds to your monthly cost. Early in the loan, most of your payment goes to interest. As the years pass, more of your payment goes toward the principal. This process is called amortization. You can view the full month-by-month breakdown using our mortgage amortization calculator.
How Extra Payments Help
If you pay extra money each month, that extra amount goes straight to your principal. This means you owe less, so the bank charges you less interest going forward. Over time, even a small extra payment each month can save you a lot of money and help you pay off your home years sooner. Our early mortgage payoff calculator lets you model exactly how quickly you can become debt-free. Another popular strategy is switching to biweekly payments, which effectively adds one extra payment per year without changing your budget much.
Why Loan Term Matters
The loan term is how many years you have to pay back the loan. A 30-year mortgage has lower monthly payments than a 15-year mortgage, but you end up paying much more interest over time. A shorter term costs more each month but saves you money in total interest paid. Before choosing a term, make sure your total debt obligations are manageable by checking your debt-to-income ratio. You should also factor in closing costs and property taxes when budgeting for your home purchase. If you are weighing whether buying makes more sense than renting, our rent vs. buy calculator can help you decide.
Use the calculator above to see exactly how much interest you will pay, compare different loan terms and rates, and find out how much you can save by making extra payments each month. If you have built up equity over time, you may also want to explore a HELOC or home equity loan for future financial needs.