Mortgage Calculator

A mortgage payment is calculated the same way as any amortizing loan: a fixed monthly amount split between principal and interest, with the interest share highest at the start and shrinking as the balance is paid down. Over a 15 or 30-year term, that front-loaded interest adds up to a substantial share of the total cost — which is exactly what the principal-vs-interest chart above is designed to make visible at a glance.

This calculator covers principal and interest only. Your actual monthly housing cost will typically be higher once property taxes, homeowners insurance, and — if your down payment is under 20% — private mortgage insurance are added on top. Use the figure here as the core loan cost, then layer your local tax and insurance estimates on top for a full picture.

A $300,000 mortgage at 6.5% over 30 years produces a monthly payment of roughly $1,896, with total interest over the full term reaching approximately $382,633 — more than the original loan amount, which is typical for a 30-year mortgage at this rate.

Switching the same $300,000 loan to a 15-year term raises the monthly payment to around $2,614 but cuts total interest to roughly $170,447 — a savings of over $212,000 for about $718 more per month, which is usually the single biggest cost-saving decision available to a mortgage borrower.