Amortization Schedule Calculator

An amortization schedule is a complete payment timeline for your mortgage. It lists every monthly payment from day one through final payoff, showing exactly how each dollar is split between principal and interest. At closing, your lender provides a static amortization schedule based on your rate and term. But any change, like an extra principal payment or a rate adjustment on an ARM, instantly invalidates that original schedule. This calculator generates a fresh schedule for any scenario you enter.

The key insight from an amortization schedule is that your payment stays the same but its composition changes dramatically over time. In month one, roughly 85% of your payment may go to interest and only 15% to principal. By year 20 of a 30-year loan, that ratio flips. Understanding this shift helps you make smarter decisions about extra payments, refinancing, or holding the loan to term.

A standard amortization table has five columns:

• Month. The payment number, starting at month 1 and ending at month 360 for a 30-year loan.
• Payment. Your fixed monthly principal and interest payment. This number stays the same for the full term of a fixed-rate loan.
• Principal. The portion of your payment that reduces your loan balance. This amount grows each month.
• Interest. The cost of borrowing, calculated as your remaining balance multiplied by your monthly rate. This shrinks each month.
• Remaining Balance. How much you still owe after that month's payment. This should reach zero at the final month.

Use the Export CSV button to download every row and import it into a spreadsheet for side-by-side comparison with your actual loan statements.

Your monthly interest charge is: remaining balance times your monthly interest rate. In month 1 of a $300,000 loan at 6.5%, the math is $300,000 x (6.5% / 12) = $1,625. That entire $1,625 goes to the lender as interest. If your total monthly P&I is $1,896, only $271 goes toward actually paying down the loan.

By month 180, your balance has dropped to roughly $215,000. The interest charge for that month is now $215,000 x (6.5% / 12) = $1,165. That frees up $731 of your $1,896 payment to go toward principal. The interest portion declines every single month because the balance it is calculated on declines every single month.

This is just how amortization works. The bank charges interest on money you still owe. You owe more in the beginning, so the interest charge is higher. The only way to reduce total interest is to pay down the principal faster, either through extra payments or a shorter loan term.

Any extra payment applied to principal reduces your balance immediately and permanently. Because interest is calculated on the remaining balance, a lower balance means less interest every month going forward. That means more of every future payment goes to principal, which accelerates the entire payoff timeline.

There are two main ways to apply extra principal. First, you can add a fixed extra amount to your monthly payment. On a $300,000 30-year loan at 6.5%, adding $200 per month saves about $90,000 in interest and pays off the loan roughly 6 years early. Second, you can apply a one-time lump sum. A $20,000 lump sum applied in year 5 saves roughly $45,000 in interest without changing your monthly payment. Use our recast calculator if you want that lump sum to also permanently lower your monthly obligation.

Warning: some lenders only apply extra payments to future interest or hold them in suspense. Make sure to specify that extra amounts should be applied to principal. Check your next statement to confirm.

Enter your loan amount, interest rate, and term. The calculator immediately generates:

• Your fixed monthly P&I payment
• A chart showing how principal and interest portions shift over the full loan term
• The crossover point where more of each payment goes to principal than interest
• Total interest cost and how it compares to your original loan amount

Adjust the term to see the difference between 30, 20, 15, and 10 year amortization. Adjust the rate to model different market conditions or rate quotes. All calculations run in your browser. No data is sent anywhere.