Loan Amortization Payment Calculator
Compute the level payment that fully amortizes a loan using the standard annuity payment formula, plus total interest paid over the term.
How it works
PMT = P · i / [1 − (1 + i)^−n] · i = annual rate ÷ m · n = years × m
A fully amortizing loan is paid off by a stream of equal payments; this formula finds the payment size so the balance reaches exactly zero on the last payment. Early payments are mostly interest and later ones mostly principal, but the payment itself never changes. It is the same annuity mathematics that powers mortgage, auto and student-loan payments.
Worked example
On a $200,000 loan at 6% annual (0.5% monthly) over 30 years (360 payments): PMT = 200,000 · 0.005 / [1 − 1.005^−360] = 1,000 / 0.83229 = $1,199.10 per month. Over 360 payments that totals $431,676, of which $231,676 is interest.
Sources: Amortization calculator — Wikipedia
Frequently asked questions
Why is so much of an early payment interest?
Interest each period is charged on the outstanding balance, which is highest at the start. As the balance falls, the interest portion shrinks and the principal portion grows, even though the total payment stays level.
What happens if the interest rate is 0%?
With no interest the payment is just the loan amount divided by the number of payments, and total interest is zero. This calculator handles the 0% case directly instead of dividing by zero.
How do extra payments change things?
Any payment above the scheduled amount goes straight to principal, which lowers all future interest and shortens the term. This calculator shows the baseline level payment; paying more than that always saves interest.
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Educational financial-math tool, not investment or financial advice.