Amortization Calculator
See your monthly payment and exactly how each one splits between interest and principal over the life of the loan.
Your loan
Works for any fixed-rate loan: mortgage, auto, personal, student
The total amount borrowed.
The loan's fixed annual interest rate.
How many years to pay it off.
Your payment
Monthly payment and total cost
Monthly payment
$1,896.2
Total interest paid
$382,633.47
Total paid over loan
$682,633.47
Interest as a share of total paid
56%
Remaining balance over time
How the loan pays down month by month
Why early payments are mostly interest
How this amortization calculator works
For example, a $300,000 loan at 6.5% over 30 years runs about $1,896.2 a month, with total interest over the life of the loan close to $382,633.47, more than the amount borrowed. Amortization means each payment splits between interest, calculated on the remaining balance, and principal, which actually reduces what's owed.
Early on, the balance is largest, so interest takes the biggest bite of each payment. As the balance shrinks, more of each payment goes toward principal instead. That is why an extra payment made early in a loan does more to shorten it than the same extra payment made later.
Why the payment stays the same but the split does not
A fixed-rate loan charges the same interest rate for the whole term, and the monthly payment is set once at the start so it never changes. What changes underneath it is the balance the interest is calculated on. Month one, interest is calculated on nearly the full loan amount. Ten years in, interest is calculated on whatever is left, which is smaller, so a bigger share of that same payment goes to principal.
This is the part people miss when they look at a 30-year mortgage and assume the halfway point means half the loan is paid off. It usually is not. Because the early payments lean so heavily toward interest, the balance drops slowly at first and faster later, so year 15 of a 30-year loan is well behind the halfway mark on principal paid down.
What extra payments actually do
An extra payment goes entirely to principal, since the interest for that period is already covered by the regular payment. Paying extra lowers the balance the very next month's interest gets calculated on, and that effect compounds for every remaining month of the loan. A single extra payment made in year one removes far more future interest than the same extra payment made in year twenty, because it has more months left to keep shrinking the balance it touches.
Check with your lender before sending extra money. Some loans apply an extra payment to next month's payment instead of the principal unless you specify it, which defeats the purpose entirely.
Reading your own amortization schedule
Your lender's amortization schedule shows this month by month: how much of each payment covered interest, how much reduced principal, and what the balance was afterward. Pull up your own schedule and compare payment one against a payment from year 10 or 15. The gap between the interest and principal portions closes gradually, then quickly toward the end of the loan, and seeing your real numbers makes the pattern above concrete instead of abstract.
How this is calculated
It splits every payment on a fixed-rate loan into interest (on the remaining balance) and principal (which pays the loan down).
Monthly payment = loan amount × monthly rate ÷ (1 − (1 + monthly rate) raised to the power of −number of payments). Each month, that month's interest is the remaining balance × the monthly rate; the rest of the payment reduces principal, so the balance shrinks and next month's interest is smaller.
What it assumes
- The interest rate is fixed for the full term. Variable-rate loans will differ.
- Payments are made on schedule every month with no skips or extra payments.
- No taxes, insurance, or fees are included. This is principal and interest only.
Frequently asked questions
Why does so little of an early payment go toward principal?
Interest is charged on the remaining balance, which is largest at the very start of the loan, so the biggest share of each early payment covers that interest. As the balance shrinks over time, less of each payment goes to interest and more goes to principal, even though the total payment stays the same.
Does an extra payment save more money early or late in a loan?
Early. An extra payment made early reduces the balance while it's still large, cutting interest for every remaining month of the loan. The same extra payment made near the end saves far less, since there's less remaining term left for a lower balance to matter.
Is this the same as a mortgage calculator?
The core math is the same, but this calculator is loan-type agnostic: no property taxes, insurance, or PMI. For a home loan specifically, including those extra housing costs, use the dedicated mortgage calculator instead.
Results are estimates for educational purposes only, based on the values you enter and a constant rate of return. Real markets rise and fall, so your actual results will differ. This is not financial advice.