What is an amortization schedule?
An amortization schedule is the full breakdown of every payment over the life of a loan — how much of each payment goes to interest, how much goes to principal, and what balance remains afterward. Your monthly payment stays the same on a fixed-rate loan, but the split between interest and principal shifts every month.
Why early payments are mostly interest
Interest is charged on your current balance, and your balance is highest at the very start of the loan. That means the interest portion of your payment is largest in the early years and shrinks every month as the balance comes down — while the principal portion does the opposite, growing larger over time. This is normal for every fixed-rate loan, not just mortgages.
How extra payments change the schedule
Add an extra monthly amount above and the table updates to show a shorter schedule with less total interest — every extra dollar goes straight to principal. If you want a side-by-side comparison of "with extra payments" vs. "without," our extra mortgage payment calculator is built specifically for that. For the base monthly payment math, see the mortgage calculator.