How the Mortgage Calculator works
Calculate your monthly mortgage payment and total cost. Adjust the inputs above, then use the calculate button to generate a fresh estimate based on the numbers you entered.
The result is designed to give you a quick planning number, plus a short breakdown of the major figures behind it. You can reset the form at any time and try a different scenario.
When to use this calculator
Use this mortgage calculator when you want a quick estimate of the monthly payment for a home purchase. It is most useful before you talk to a lender, compare homes, or test how a larger down payment changes the payment. The estimate focuses on principal and interest, so you should still budget separately for property tax, insurance, condo fees, utilities and maintenance.
Formula
Mortgage payment = P x r(1 + r)^n / ((1 + r)^n - 1)
- P is the mortgage principal after your down payment.
- r is the monthly interest rate, which is the annual rate divided by 12.
- n is the total number of monthly payments over the amortization period.
Worked example
For a $500,000 home with a $100,000 down payment, the mortgage balance is $400,000. At 5% over 25 years, the calculator estimates the monthly principal and interest payment and the total paid over the full amortization.
Common mistakes
- Forgetting that property tax, insurance and closing costs are not included in the principal and interest payment.
- Using the posted rate instead of the rate you expect to qualify for.
- Choosing the longest amortization only because the monthly payment looks lower, without checking total interest.
FAQs
Does this include property tax or insurance?
No. This calculator focuses on principal and interest. Add property tax, home insurance, utilities and other housing costs separately.
Why does the down payment matter so much?
A larger down payment lowers the mortgage balance, which can reduce both the monthly payment and the total interest paid.
Is this the same as a lender approval?
No. Lenders also review income, credit, debts, property details and underwriting rules. Treat this as a planning estimate.