How to use the Mortgage Calculator
A mortgage calculator shows the monthly cost of a home loan and how much interest you will pay over its life. Use it before you view homes, to check what you can afford, and again when you compare lenders.
Open the Mortgage Calculator →
What you need to enter
- Home price ($)
- Down payment (%)
- Loan term (years)
- Interest rate (%)
- Property tax ($ / year)
- Home insurance ($ / year)
- HOA / other ($ / month)
The formula
Monthly principal and interest = P × r ÷ (1 − (1 + r)^−n), where P is the loan amount, r is the monthly interest rate (annual rate ÷ 12) and n is the number of monthly payments. Property tax and insurance are added on top.
Worked example
Using the default values in the calculator:
- Home price ($): 400000
- Down payment (%): 20
- Loan term (years): 30
- Interest rate (%): 6.5
- Property tax ($ / year): 4800
- Home insurance ($ / year): 1500
- HOA / other ($ / month): 0
| Total monthly payment | $2,547.62 |
| Principal & interest | $2,022.62 |
| Property tax | $400.00 |
| Home insurance | $125.00 |
| Loan amount | $320,000.00 |
| Total interest | $408,142.36 |
Tips for better results
- Try a few down payments: a bigger deposit lowers both the payment and the total interest.
- Add property tax, home insurance and any HOA fees, because they can add hundreds a month.
- Compare 15-year and 30-year terms to see the trade-off between a higher payment and lower interest.
Common mistakes to avoid
- Forgetting taxes, insurance and maintenance, so the real monthly cost is higher than the quote.
- Comparing loans only by monthly payment instead of total interest and fees.
Please note: Calculators and guides give general estimates, not financial, tax or investment advice. Real offers depend on your lender, location and personal situation. See our Disclaimer.