What Is a Mortgage Amortization Calculator?
A mortgage amortization calculator shows how each monthly payment is split between principal and interest. It helps you understand how much of your payment reduces the loan balance versus how much goes to interest, especially in the early years of the loan.
How to Use This Mortgage Amortization Calculator
- Enter the total loan amount.
- Enter the annual interest rate as a percentage.
- Enter the loan term in years.
- Click “Calculate” to see your monthly payment, the first payment’s principal and interest breakdown, and the total interest over the life of the loan.
Key Concepts
Amortization means spreading loan repayment over fixed periodic payments. In early years, most of each payment goes toward interest; in later years, the majority goes to principal. On a 30-year $300,000 mortgage at 6.5%, the first payment allocates roughly $1,625 to interest and only $270 to principal. By year 20, this ratio reverses. Understanding this shift helps you make strategic decisions about extra payments and refinancing.
Interest = Balance × Monthly Rate
Principal = Payment − Interest
Frequently Asked Questions
Why does so much go to interest at the beginning?
Interest is calculated on the outstanding balance. Since the balance is highest at the start, interest charges are largest early on. As you pay down principal, interest decreases and more of each payment reduces the balance—this accelerates over time.
How do extra payments affect amortization?
Extra payments go entirely toward reducing principal, which decreases future interest charges on every subsequent payment. Even small extra payments in the early years have a disproportionately large impact on total interest saved and payoff date. You can use the first payment breakdown shown by this tool to understand how much of your payment currently goes to interest.
When does it make sense to refinance?
Consider refinancing when rates drop 0.75%–1.0% below your current rate, you plan to stay in the home long enough to recoup closing costs, or you want to switch from an adjustable to a fixed-rate mortgage for payment stability.