Amortization is the process of spreading a loan into a series of fixed payments over time. Each payment covers some interest and some principal, but the ratio shifts dramatically as the loan matures — early payments are almost entirely interest, while later payments chip away at the balance itself.

Enter your loan details below to see your monthly payment and a complete month-by-month breakdown.

How Amortization Works

When you take out a fixed-rate loan, your lender calculates a monthly payment that, if made consistently, will pay off both the interest and the principal by the end of the term. The math behind it uses a standard formula: M = P[r(1+r)^n] / [(1+r)^n - 1], where P is the principal, r is the monthly interest rate, and n is the total number of payments.

What makes amortization interesting — and sometimes alarming — is how the payment composition changes over time. On a typical 30-year mortgage, you might spend the first decade paying more in interest than principal each month. It's only in the back half of the loan that the balance starts dropping noticeably.

Reading the Amortization Schedule

The schedule table shows five columns for each month of your loan: the payment number, total payment amount, how much goes to principal, how much goes to interest, and the remaining balance. Scroll through it to see how those ratios shift. Early in the loan, the interest column dominates. As you progress, more of each payment erodes the principal.

Why Extra Payments Matter

One of the most powerful takeaways from an amortization schedule is seeing how extra payments accelerate payoff. Even small additional principal payments — an extra $100 or $200 a month — can shave years off a mortgage and save tens of thousands in interest. That's because the extra payment goes entirely toward principal, reducing the balance that future interest is calculated on.

15-Year vs. 30-Year: The Trade-Off

A 15-year mortgage comes with a higher monthly payment but a significantly lower total interest cost. Try running both scenarios through the calculator to see the difference. For many borrowers, the 15-year option saves six figures in interest — but the higher payment can strain monthly cash flow. There's no universally right answer; it depends on your income stability, other financial goals, and how much flexibility you need in your budget.

Common Loan Types This Calculator Covers

While most people think of amortization in the context of mortgages, the same math applies to any fixed-rate installment loan: auto loans (typically 3-7 years), student loans on a standard repayment plan (10 years), and personal loans (usually 2-5 years). If it has a fixed rate and a set number of payments, this calculator will give you an accurate schedule.