Amortization is the process of spreading a loan into a series of fixed payments over time, where each payment covers both interest and a portion of the principal balance.
How Amortization Works
When you take out a mortgage or car loan, your monthly payment stays the same for the life of the loan. But the split between principal and interest shifts dramatically over time. In the early years, most of your payment goes toward interest. In the later years, most goes toward principal.
This front-loaded interest structure means that borrowers who sell or refinance early may find they have paid mostly interest and reduced very little principal.
The Amortization Formula
The monthly payment is calculated as: M = P × [r(1+r)^n] / [(1+r)^n − 1], where:
- M = monthly payment
- P = loan principal
- r = monthly interest rate (annual rate ÷ 12)
- n = total number of payments
Why Amortization Matters
Understanding amortization helps borrowers make smarter decisions about extra payments, refinancing, and loan terms. Even small extra payments applied to principal in the early years can save tens of thousands in interest and shorten the loan by years.
Real-World Example
A $300,000 mortgage at 6.5% for 30 years has a monthly payment of $1,896. In month one, $1,625 goes to interest and only $271 to principal. By month 300 (year 25), only $185 goes to interest and $1,711 to principal. Total interest paid over 30 years: $382,633.
Frequently Asked Questions
What is an amortization schedule?
An amortization schedule is a complete table showing every payment over the life of a loan, broken down into the principal and interest portions. It reveals exactly how much of each payment reduces your balance.
How do extra payments affect amortization?
Extra payments go directly toward principal, reducing the balance faster. This means less interest accrues in future periods, which can shorten a 30-year mortgage by 5-10 years and save tens of thousands in interest.
Is amortization the same as depreciation?
No. Amortization refers to spreading loan payments over time (or writing off intangible assets). Depreciation refers to the declining value of tangible physical assets like equipment or vehicles over their useful life.