Calculate your monthly repayment, total interest, and cost over the loan term.
Multiply your loan amount by [r(1+r)^n] ÷ [(1+r)^n − 1], where r is your monthly interest rate (annual rate ÷ 12) and n is total payments (years × 12). On a $400,000 loan at 6.5% for 30 years, the monthly payment is $2,528.
Your monthly mortgage payment depends on three things: the loan amount (principal), the annual interest rate, and the loan term. The standard formula is M = P[r(1+r)^n] / [(1+r)^n - 1], where r is your monthly interest rate and n is the total number of monthly payments. This calculator handles the math and generates a full year-by-year amortisation table.
On a $400,000 mortgage at 5.5% over 25 years, the monthly payment is about $2,449 — but the total paid over the life of the loan is around $734,700. That's $334,700 in interest on top of the $400,000 principal. A lower rate or shorter term dramatically reduces this total. Reducing the term from 25 to 20 years at the same rate saves roughly $80,000 in interest.
In the early years of a mortgage, most of each payment goes to interest rather than reducing the loan balance. As the balance falls, the interest portion shrinks and more of each payment goes to principal. The amortisation table below the calculator shows this split year by year, which helps you understand how much equity you're building each year.
A shorter loan term means higher monthly payments but far less total interest. A longer term reduces monthly outgoings but increases the total cost significantly. Use the calculator to compare terms side by side — the difference in total interest between a 15-year and 30-year mortgage on the same loan is often six figures.