Amortization Calculator (Yearly Schedule & Extra Payments)

The formula behind the schedule

Every fixed-rate loan uses the same equation: the monthly payment equals the loan amount times r(1+r)^n divided by ((1+r)^n minus 1), where r is the monthly rate and n the number of payments. That payment is engineered so the balance lands on exactly zero at the final month. Amortization is what happens inside it: interest is charged on the remaining balance first, and only the remainder retires principal. Because the balance starts large, early payments are interest-heavy; because it ends small, late payments are almost all principal. The schedule in the calculator is just that arithmetic repeated month after month and rolled up by year.

Reading a real schedule: $280,000 at 6.75%

Borrow $280,000 over 30 years at 6.75% and the payment is about $1,816. The first month splits into $1,575 of interest and only $241 of principal. Fifteen years in, at the loan's halfway mark, you still owe about $205,000: nearly three quarters of the original balance. The crossover where principal finally outweighs interest arrives late, and total interest reaches roughly $374,000, more than the amount borrowed. None of this is a trick; it's what charging interest on a slowly falling balance looks like. The mortgage calculator runs the same math from the home price and down payment side instead of the loan amount.

Where a schedule changes decisions

Seeing the split matters most at three moments. Comparing terms: a 15-year schedule front-loads principal so aggressively that total interest often falls by more than half versus a 30-year. Deciding on extra payments: because prepaid dollars skip the interest split entirely, even $200 a month on the $320,000 default here removes about $105,000 of interest and ends the loan six and a half years early, which the mortgage payoff calculator explores in depth. And building equity: the balance column tells you what you'd still owe if you sold in any given year, which is the number your equity grows against. For any loan you already hold, the loan payoff calculator starts from today's balance instead of the original one.