This amortization calculator shows the full schedule of your loan, and how each payment splits between principal and interest.
Written by Renzo Johnson, Licensed Mortgage Loan Originator · Last updated: August 2026
- Enter: loan amount, interest rate, term, start date
- See: the full payment schedule, total interest, and the payoff date
- Test: extra monthly principal, annual lump sums, and a shorter term
- Interactive calculator coming soon.
Why the early years look the way they do
Your payment stays level, but its composition does not. Interest is charged on the balance you still owe, so at the start almost all of the payment covers interest and very little touches principal.
On a 30-year loan the crossover, where principal finally exceeds interest in a single payment, usually arrives somewhere past year eighteen. That is the fact an amortization calculator makes visible, and it is why the first years of a mortgage build equity slowly.
What extra principal actually does
Any dollar you add to principal removes all the future interest that dollar would have carried. The effect is largest early, because that is when the balance is largest.
Test a modest extra payment in the schedule and watch the payoff date rather than the monthly figure. A small addition applied from the beginning often removes several years from the term. Make sure your servicer applies it to principal, since otherwise it is held as a prepayment of the next instalment and does nothing.
Term length is the other lever
| Term | Monthly payment | Total interest |
|---|---|---|
| 30 years | Lowest | Highest, by a wide margin |
| 15 years | Higher | Far lower, and usually at a lower rate |
A shorter term is not automatically better. It commits you to the higher payment, whereas a 30-year loan with voluntary extra principal keeps the choice in your hands each month. Read 15-year versus 30-year before you decide.
A Florida footnote
The schedule covers principal and interest only. Your actual payment also carries taxes, insurance and any association dues, and in Florida the insurance portion can move sharply at renewal. Budget from the full payment, not from the amortization line.
Get pre-qualified and we will run your real schedule against the programs you qualify for.