Written by FreeToolCalc Team
Formulas based on standard financial/medical equations. Last updated: March 2026.
How to use a mortgage calculator
A mortgage calculator helps you turn a home price into a real monthly payment. That matters because house shopping usually feels very different once you see the payment tied to the loan amount, interest rate, and loan term.
Mortgage payment formula
Lenders use the standard amortization formula to calculate a fixed monthly payment over the life of the loan.
M = P[r(1+r)^n] / [(1+r)^n - 1]
P = principal, r = monthly interest rate, n = total number of payments
Example mortgage payments
| Loan Amount | Rate | Term | Approx. Payment |
|---|---|---|---|
| $250,000 | 6.5% | 30 years | $1,580 |
| $350,000 | 6.5% | 30 years | $2,212 |
| $350,000 | 6.0% | 15 years | $2,953 |
What changes your mortgage payment most
- Loan amount: A larger loan raises the payment.
- Interest rate: Even a small rate increase matters.
- Loan term: Longer terms lower the payment but raise total interest.
- Down payment: A bigger down payment reduces the balance you finance.
Important: Use this mortgage calculator as a planning tool. Your final lender quote can differ because of taxes, insurance, fees, points, and PMI.