Guide · Debt
How Amortization Works: Reading a Loan Schedule Like a Lender
Every fixed-rate loan — mortgage, auto loan, or personal loan — follows the same amortization math. Understanding it explains why your balance moves the way it does, and how to pay less interest overall.
The shifting interest/principal split
On a $300,000 loan at 6.5% over 30 years, the very first payment is almost entirely interest. By the final years, almost the entire payment reduces principal:
| Payment # | Interest | Principal |
|---|---|---|
| 1 | $1,625 | $271 |
| 180 (year 15) | $1,121 | $775 |
| 360 (final) | $10 | $1,886 |
How extra payments compound
Because each extra dollar of principal you pay off stops accruing interest immediately — and every month after — small overpayments snowball into large savings over a long loan term.
Reading your own schedule
Look for three things on any amortization schedule: the payment date, the interest/principal split for that period, and the running balance. If you're considering an extra payment or refinance, compare the remaining balance and the cumulative interest already paid against what a new schedule would look like.
Frequently asked questions
Why is so much of my early payment interest?
Interest is calculated on the outstanding balance each period. Early on, the balance is at its highest, so the interest charge is largest — leaving less of your fixed payment to reduce principal. As the balance falls, the interest charge shrinks and more of each payment chips away at principal.
Does making one extra payment a year actually help much?
Yes — because extra payments go straight to principal, they reduce the balance that all future interest is calculated on. One extra mortgage payment a year can shave several years off a 30-year term and save tens of thousands in interest, depending on the rate and balance.
Why does my balance barely move in the first few years of a mortgage?
On a long-term, low-rate loan, the early payments are so interest-heavy that principal reduction is slow at first. This is normal — the curve accelerates over time as the balance (and therefore the interest charge) shrinks.
What's the difference between amortizing and interest-only loans?
An amortizing loan's fixed payment includes both interest and principal, so the balance reaches zero by the end of the term. An interest-only loan's payment covers interest only — the principal balance stays the same until you either start amortizing or repay it in a lump sum.