Loan Amortization Calculator with Extra Payments

How this calculation works

Amortization spreads a loan into equal monthly payments of principal + interest. Early payments are mostly interest; over the life of a 30-year mortgage at 6.5%, interest exceeds half of what you borrow.

Extra principal payments compound in your favor by reducing the balance on which future interest accrues — the earlier you make them, the larger the savings.

How this Loan Amortization Calculator with Extra Payments works — 2026 guide

A 30-year mortgage at 6.5% costs more in interest than many borrowers expect — on a $350,000 loan it is roughly $446,000 in interest alone. This amortization calculator shows your exact monthly principal-and-interest payment, the total interest over the full term, and — the part most calculators skip — what an extra monthly payment does to your payoff date and total interest. It works for mortgages, auto loans, and personal loans alike.

How to use it in 3 steps

1. Enter the loan amount, annual interest rate, and term in years.
2. Optionally add an extra monthly principal payment.
3. Read your monthly P&I, lifetime interest, payoff time, and interest saved.

Who this is for

Home buyers comparing lenders, homeowners deciding whether to prepay, and car buyers choosing between loan terms. Pair with the [home affordability calculator](/tools/home-affordability-calculator/) to size the loan you can actually carry.

Data sources & authoritative references

This calculator is built on official U.S. rules and published statistics. Key sources:

• Federal Reserve — 30-year fixed-rate mortgage averages
• Consumer Financial Protection Bureau — Mortgage loan amortization
• IRS — Deducting mortgage interest