Understanding Amortization Schedules: How Loan Payments Work
Learn how amortization schedules break down each loan payment into principal and interest. See how extra payments save money and shorten your loan term.
What Is an Amortization Schedule
An amortization schedule is a table that shows exactly how each loan payment is divided between principal and interest over the entire life of the loan. Every row represents one payment period (usually monthly) and includes the payment amount, the interest portion, the principal portion, and the remaining loan balance. At the start of the loan, a larger share of each payment goes toward interest. Over time, the interest portion shrinks and the principal portion grows, even though your total payment stays the same. This front-loading of interest is why early extra payments are so powerful — they reduce the principal faster and save the most interest over the life of the loan.
How Interest Is Calculated Each Month
For a standard amortizing loan, each month's interest is calculated by multiplying the outstanding balance by the monthly interest rate. Monthly rate equals your annual rate divided by 12. For example, on a $250,000 mortgage at 6.5 percent: monthly rate is 0.065 / 12 = 0.005417. Your first month's interest is $250,000 times 0.005417 = $1,354.17. If your total monthly payment is $1,580.17, then $1,354.17 goes to interest and only $226 goes to principal. After that payment, your balance drops to $249,774 and next month's interest is slightly less. This gradual shift is the essence of amortization.
The Power of Extra Payments
Making extra payments directly reduces your principal balance, which means less interest accrues in every subsequent month. On a $300,000, 30-year mortgage at 6.5 percent, an extra $200 per month saves approximately $102,000 in total interest and pays off the loan 7 years early. Even one extra payment per year — made by paying half your monthly amount every two weeks instead of the full amount monthly — can shave 4 to 5 years off a 30-year mortgage. When making extra payments, specify that the additional amount should be applied to principal, not to the next month's payment.
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Types of Amortization
Fully amortizing loans — like most fixed-rate mortgages and auto loans — are designed so that equal payments over the term completely pay off the loan. Interest-only loans require you to pay only the interest for a set period (usually 5 to 10 years), after which payments jump because you must then amortize the full principal over the remaining term. Negative amortization occurs when your payment does not cover the interest due, causing the loan balance to grow — this is rare and risky. Balloon loans amortize normally but require a large lump-sum payment at the end. Understanding which type you have is critical to planning your finances.
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Frequently Asked Questions
Why does so little of my early payments go to principal?
Because interest is calculated on the outstanding balance, and early in the loan that balance is at its highest. On a $300,000 mortgage at 6.5 percent, your first payment has about $1,625 in interest and only $270 in principal. As you pay down the balance, the interest portion decreases and the principal portion increases. By the final years, nearly all of each payment goes to principal.
Is it better to make extra payments or refinance?
It depends on interest rates and your timeline. If current rates are significantly lower than your existing rate, refinancing can reduce your monthly payment and total interest. If rates are similar or higher, making extra payments on your current loan is more effective. Extra payments cost nothing beyond the money itself, while refinancing involves closing costs of 2 to 5 percent of the loan amount.
Do all loans amortize the same way?
No. Fixed-rate loans have predictable amortization schedules. Adjustable-rate mortgages (ARMs) have schedules that change when the interest rate adjusts. Credit cards and lines of credit use revolving credit, not amortization. Student loans may offer income-driven repayment plans that modify the standard amortization schedule based on your earnings.