Economics
Loan Amortization
Quick fact
On a typical 30-year mortgage, you may pay more in total interest than the original loan amount, even though each payment is the same size.
Why this is interesting
You sign up for a car loan and make the same monthly payment every month. But did you know that in the early years, most of that payment goes to interest, not the car itself?
Read the full explanation
Understanding Loan Amortization
Imagine renting a house: every month you pay rent, but you never own it. Now imagine a loan that lets you slowly buy the house while paying rent on the part you haven't bought yet. Amortization is that process. You agree to a fixed monthly payment. Each payment is split into two parts: interest (the 'rent' on the money you still owe) and principal (the part that actually reduces your debt). Early on, you owe a lot, so the interest portion is large. As you pay down the principal, the interest shrinks, so more of your payment goes toward owning the asset. This is why amortization feels slow at first—you're mostly paying interest—but accelerates later as the principal shrinks faster.
A deeper explanation
Loans are amortized using a mathematical formula that ensures each fixed payment exactly covers the interest due and pays off the entire principal by the end of the term. The interest for each period is calculated on the remaining principal balance. Since the principal declines, the interest portion decreases over time, allowing more of the payment to go toward principal. This process is governed by the amortization schedule, which lists every payment and shows the split. An amortizing loan differs from an interest-only loan, where you never reduce the principal unless you pay extra. Amortization is crucial because it gives borrowers a clear path to full ownership, and lenders a predictable, lower-risk return. Understanding the mechanism helps you see why making extra principal payments early can save enormous amounts of interest over the life of a loan.