Mortgage Calculator
Estimate the monthly payment, total interest, and total cost of a fixed-rate mortgage.
How to use this calculator
- Enter the loan amount — the home price minus your down payment.
- Enter the annual interest rate as a percentage (for example 6.5, not 0.065).
- Enter the term in years and press Estimate payment.
The formula
M = P × r(1 + r)ⁿ ÷ ((1 + r)ⁿ − 1)- M
- Monthly payment
- P
- Principal (amount borrowed)
- r
- Monthly interest rate = annual rate ÷ 12 ÷ 100
- n
- Total number of monthly payments (years × 12)
How it works
A fixed-rate mortgage is amortizing: every monthly payment is identical, but early payments are mostly interest while later payments are mostly principal.
The formula sizes the payment so that, after n payments with interest accruing monthly on the remaining balance, the balance reaches exactly zero.
Worked example
A $300,000 loan at 6.5% for 30 years.
- 1r = 6.5 ÷ 12 ÷ 100 ≈ 0.005417
- 2n = 30 × 12 = 360
- 3M = 300,000 × 0.005417 × (1.005417)³⁶⁰ ÷ ((1.005417)³⁶⁰ − 1)
M ≈ $1,896.20 per month; total interest ≈ $382,633 over the life of the loan.
When this calculator is useful
- Comparing 15-year vs 30-year terms
- Estimating affordability before talking to a lender
- Seeing how rate changes affect the payment
- Estimating total interest cost
Frequently asked questions
Why is so much of the early payment interest?
Interest each month is charged on the outstanding balance. At the start the balance is largest, so the interest share is largest.
How much does a 15-year term save?
The monthly payment rises roughly 40–50%, but total interest typically falls by more than half because the balance shrinks much faster.
Does this include taxes and insurance?
No. Add your estimated property tax, insurance, and any PMI to the result for a realistic housing budget.