How to Read an Amortization Schedule
An amortization schedule breaks every mortgage payment into its principal and interest components. In the early years, most of your payment covers interest. By the final years, almost every dollar retires principal. Understanding the schedule helps you see the true cost of borrowing and the power of extra payments.
What Is an Amortization Schedule?
An amortization schedule is a complete table of every scheduled loan payment from the first month to the last. Each row shows exactly how much of that month's payment goes to interest, how much reduces the loan balance (principal), and what the remaining balance is after the payment. For a 30-year mortgage, that is 360 rows — one per month.
What Each Column Means
A standard mortgage amortization schedule has five columns:
Payment number — The sequential month (1 through 360 for a 30-year loan).
Payment amount — Your fixed monthly payment. For a $400,000 loan at 7% over 30 years, the monthly payment is $2,661.
Interest portion — The monthly interest charge, calculated as (remaining balance × annual rate) ÷ 12. In Month 1: ($400,000 × 0.07) ÷ 12 = $2,333.
Principal portion — What remains after paying the interest. In Month 1: $2,661 − $2,333 = $328.
Remaining balance — The new loan balance after the principal is applied. After Month 1: $400,000 − $328 = $399,672.
Generate Your Amortization Schedule
See exactly how every payment splits between principal and interest
How the Schedule Shifts Over Time
The math creates a slow but steady shift. Because the remaining balance shrinks each month, the interest charge also shrinks. That frees up more of the fixed payment to retire principal, which further shrinks the balance — a compounding effect that accelerates near the end.
On the same $400,000 loan at 7%:
- Month 1: $2,333 interest / $328 principal
- Month 60 (Year 5): ~$2,267 interest / ~$394 principal
- Month 180 (Year 15): ~$1,987 interest / ~$674 principal
- Month 360 (Year 30): ~$18 interest / ~$2,643 principal
Over the full 30 years, you will pay roughly $558,000 in total — meaning about $158,000 goes purely to interest on a $400,000 loan.
Why This Matters for Your Finances
Reading your amortization schedule early makes you a smarter borrower. You will see that refinancing in year 3 versus year 15 has very different implications — by year 15 you have already paid the bulk of the front-loaded interest. You will also see why even a single extra payment per year can cut years off your loan and save tens of thousands of dollars.
Key Takeaways
- Each month's interest charge equals the current balance multiplied by the monthly interest rate.
- Early payments are interest-heavy; later payments are principal-heavy.
- On a $400,000 / 7% / 30-year loan, Month 1 interest is $2,333 while Month 360 interest is only ~$18.
- The total interest paid over 30 years can exceed 40% of the original loan amount.
Why do early mortgage payments go mostly toward interest?▾
Because interest is calculated on the outstanding balance. Early in the loan, the balance is highest, so interest charges are highest. As you pay down principal, the balance drops and more of each payment chips away at principal.
Can I use an amortization schedule to decide whether to make extra payments?▾
Yes. An amortization schedule shows you exactly how much interest you will pay over the life of the loan. By comparing schedules with and without extra payments, you can see the interest savings and how many months you cut from the term.