This calculator estimates your monthly mortgage payment — principal and interest only — from the home price, down payment, interest rate, and loan term. It also shows total interest and total cost over the life of the loan.
The formula
This is the standard fixed-rate amortization formula: it spreads the loan amount into equal monthly payments so that, by the final payment, the entire balance plus all accrued interest is paid off. Early payments are mostly interest; later payments are mostly principal.
Worked example
A $350,000 home with a $70,000 down payment leaves a $280,000 loan. At 6.5% APR over 30 years, the monthly principal-and-interest payment comes to about $1,770. Over the full 30-year term, you'd pay roughly $637,125 in total — meaning about $357,125 of that is interest, more than the loan amount itself.
Amortization snapshot (first year vs. last year)
| Period | Mostly goes to | Why |
|---|---|---|
| Year 1 | ~78% interest, ~22% principal | The balance is still near its highest, so interest accrues on nearly the full loan amount |
| Year 30 (final) | ~2% interest, ~98% principal | The balance is nearly paid off, so almost nothing is left to charge interest on |
Important assumptions and limitations
- Principal and interest only. Property tax, homeowners insurance, HOA dues, and PMI (if your down payment is under 20%) are not included and will add to your real monthly payment.
- Fixed rate assumed. This calculator models a fixed-rate loan. Adjustable-rate mortgages (ARMs) change over time and aren't modeled here.
- No extra payments. The result assumes you pay exactly the scheduled amount each month with no prepayments toward principal.
Curious what an extra payment could save you over the life of the loan? Try the compound interest calculator to see how extra principal payments compound in your favor, or the retirement savings estimator if you're weighing prepaying the mortgage against investing instead.
This tool provides a general educational estimate and is not financial or lending advice. Actual loan terms, rates, and required payments are set by your lender.
Frequently asked questions
Does this include property tax and insurance?
No. This calculator shows principal and interest only, which is the core of your payment. Property tax, homeowners insurance, HOA fees, and PMI are added separately by your lender and vary widely by location, so we don't estimate them here.
What down payment should I use?
There's no fixed rule. A larger down payment lowers your loan amount, your monthly payment, and your total interest, and can help you avoid PMI if it reaches 20% of the home price. A smaller down payment gets you into a home sooner but costs more over the life of the loan.
How does the loan term affect total interest?
A shorter term (like 15 years instead of 30) means a higher monthly payment but dramatically less total interest, since you're borrowing the money for less time. A longer term lowers the monthly payment but roughly doubles or triples the total interest paid over the life of the loan.