Mortgage Calculator
Enter a home price, down payment amount, annual rate and years to estimate the monthly principal-and-interest payment.
Calculator arithmetic runs locally in your browser and does not require an API.
The interactive calculator loads here when JavaScript is enabled.
How to use Mortgage Calculator
Subtract the down payment from the price to get the loan principal. Compare down payments while holding the rate and term fixed.
Formula and method
M = P × r / [1 − (1+r)^−N], where r is annual percentage / 1200 and N is months. At zero interest, M = P/N.
Understanding the results
The monthly figure covers principal and interest only. Taxes, insurance, HOA, PMI, closing costs and extra payments are excluded; it is not a complete housing budget.
Worked example
A 300,000 home with 60,000 down leaves 240,000 financed. At 6% for 30 years, the regular monthly payment is 1,438.92.
These are mathematical estimates, not financial advice or an offer of credit.
Frequently asked questions
Does the estimate include property tax?
No. Property tax, insurance, HOA and PMI must be budgeted separately.
What does a larger down payment change?
It reduces the financed principal, so payment and total interest fall if rate and term stay unchanged.
Is the rate fixed for the whole term?
Yes. Adjustable rates and refinancing are outside this model.