How this mortgage calculator works
Enter the home price, your down payment, the interest rate and the loan term. The calculator works out the monthly principal and interest with the standard amortization formula, then adds the costs most lenders collect alongside it: property tax, homeowners insurance, private mortgage insurance (PMI) and any HOA fee. Every number updates as you type, and the link in your address bar saves your inputs so you can share or bookmark the result.
The mortgage payment formula
The principal-and-interest part of the payment is
M = P × r ÷ (1 − (1 + r)−n)
where P is the amount you borrow (price minus down payment), r is the yearly interest rate divided by 12, and n is the number of monthly payments (30 years = 360). For a $320,000 loan at 6.5% over 30 years that's about $2,023 a month. Over the full term you'd pay roughly $408,000 in interest, more than the loan itself, which is why the rate and term matter so much.
Why early payments are mostly interest
Each month's interest is charged on the balance still owed. At the start the balance is at its largest, so most of the payment goes to interest and only a small slice reduces the loan. As the balance shrinks, the split flips. The chart above shows this shift year by year: orange is interest, blue is principal.
Ways to lower your payment or total cost
- Put down 20% or more to avoid PMI, which typically costs 0.3%–1.5% of the loan a year.
- Compare a 15-year term. The payment is higher, but rates are usually lower and the total interest is often less than half.
- Shop several lenders. A rate difference of 0.25% on a $320,000 loan changes the payment by about $53 a month and the total by around $19,000.
- Check the property tax rate for the exact town. It varies from under 0.5% to over 2% of the home's value depending on where you buy.
What this calculator doesn't include
Closing costs, points, and changes in tax or insurance over time aren't included, and adjustable-rate loans will change after the fixed period. Use the result as a planning estimate and confirm the details with your lender's Loan Estimate.