Mortgage Calculator

The amortization formula

A fixed-rate mortgage is repaid with equal monthly payments that cover the month's interest plus a slice of principal. The principal-and-interest payment uses the standard amortization formula: M = P × r ÷ (1 − (1 + r)⁻ⁿ). P is the loan amount, r is the monthly interest rate — the annual percentage rate divided by 12 and by 100 — and n is the total number of monthly payments. A 30-year loan has 360 payments. Early in the schedule most of each payment is interest; later, as the balance falls, more goes to principal. That changing split is exactly what the amortization table below shows, row by row.

Taxes, insurance and extra payments

Most homeowners pay more than principal and interest. Property taxes and homeowners insurance are often collected monthly into an escrow account, so this calculator divides each annual figure by twelve and adds it to the payment. Those amounts are not borrowed money, so they do not accrue mortgage interest — they simply raise the total you send each month. An optional extra payment is applied directly to principal every month. Because it skips interest entirely, even a small extra amount can remove years from the schedule and save a large share of total interest. The payoff time and table both update to reflect the shorter term.

Using the schedule for planning

Compare terms and rates to see how affordability and lifetime cost trade off. A longer term lowers the monthly payment but raises total interest, while a shorter term or extra payments do the opposite. Watch the balance column to see when you cross the halfway point, and the interest column to understand how front-loaded mortgage interest really is. Everything runs in your browser with no account, credit check or live-rate lookup, so you can model private scenarios freely. Treat the output as an estimate and confirm final numbers — including PMI, HOA dues, closing costs and any rate adjustments — with your lender before signing.