About this tool
A mortgage is the biggest financial commitment most people ever sign, and the difference between rates or terms is measured in tens of thousands. This calculator makes those trade-offs visible in seconds. Enter the loan amount, annual interest rate and term in years, and it computes the monthly principal-and-interest payment using the standard amortization formula, the total paid over the life of the loan, and the total interest — the number that usually surprises people. A live chart draws the declining balance across the term so you can see how slowly equity builds in the early years, when payments are mostly interest. Adjust any input and everything recalculates instantly, which makes it easy to compare scenarios: 15 versus 30 years, or what a quarter-point rate change is really worth. The math is exact fixed-rate amortization, done locally in your browser — your finances stay private. It covers principal and interest only; taxes, insurance and HOA fees are extra and vary by location.
How to use Mortgage Calculator
- Enter the loan amount you plan to borrow.
- Enter the annual interest rate, for example 6.5.
- Choose the term in years, typically 15 or 30.
- Read the monthly payment, total interest, and the balance-over-time chart.
Frequently asked questions
What formula does it use?
The standard fixed-rate amortization formula: payment equals principal times r times (1+r)^n over ((1+r)^n minus 1), where r is the monthly rate and n the number of payments.
Are taxes and insurance included?
No. The payment shown is principal and interest only. Property tax, insurance and HOA fees are additional and location-specific.
Why is early progress on the balance so slow?
Early payments are mostly interest because the balance is large. The chart shows the crossover point where principal starts to dominate.
Is my financial data uploaded?
No. All calculations run locally in your browser; nothing is transmitted or stored.