Mortgage Calculator | Estimate Monthly Home Loan Payments

Formula: M = P · [r(1+r)^n] / [(1+r)^n − 1]

How a mortgage payment is calculated

The standard fixed-rate mortgage uses the amortization formula M = P × [r(1+r)n] / [(1+r)n − 1] where P is the loan principal (home price minus down payment), r is the monthly interest rate (annual APR ÷ 12), and n is the total number of monthly payments (loan term in years × 12).

Example: $400,000 home, 20% down, 6.5% APR, 30 years

• P = 400,000 − 80,000 = $320,000
• r = 0.065 / 12 = 0.00541667
• n = 30 × 12 = 360 payments
• M ≈ $2,022.62 per month (principal & interest only)

Total monthly payment (PITI)

Lenders typically quote the total monthly cost as PITI: Principal, Interest, Taxes, and Insurance. The calculator above adds estimated property taxes (annual ÷ 12), homeowners insurance (annual ÷ 12), HOA dues, and PMI (if your down payment is below 20%) to give the full out-of-pocket monthly cost.

When PMI applies

Conventional loans typically require Private Mortgage Insurance when the down payment is less than 20% of the home price. PMI usually costs 0.3%–1.5% of the original loan balance per year and is automatically removed once your loan-to-value ratio (LTV) reaches 78%.

Source & review

Formula and reference values follow the published guidance from the Consumer Financial Protection Bureau (CFPB). Reviewed quarterly against the latest Loan Estimate disclosure rules.

What is the Mortgage Calculator?

The Mortgage Calculator is a free, browser-based finance calculator tool that helps you. Mortgage calculator estimates the monthly principal-and-interest payment on a home loan based on the home price, down payment, interest rate (APR), and loan t. Instead of working through the math by hand or in a spreadsheet, you enter your values and the calculator returns an accurate result instantly — while still showing the formula and the steps so you can verify the reasoning. It is designed for quick everyday use: no sign-up, no installation, and everything runs locally in your browser for complete privacy.

How to use the Mortgage Calculator

1. Enter the required values into the input fields.
2. Press the calculate button — the result appears immediately, updated live as you change any value.
3. Read the step-by-step breakdown below the result to see exactly how the calculation was performed.
4. Use the interpretation guide to understand what the result means for your situation, and try different inputs to see how they change the outcome.

How to use the Mortgage Calculator

Start with the home price and the down payment you plan to make — 20% or more avoids PMI. Enter the annual interest rate (APR) and the loan term in years, then add property tax, home insurance, and HOA dues if you know them, so the result reflects the full PITI payment, not just principal and interest. Run the same inputs with a 15-year term to see how much extra monthly cost buys you a massively lower lifetime interest bill.

Interpreting your result

The monthly payment line is what the lender will expect, but the total-interest line is the number that should drive your decision. On a $400,000 home with 20% down at 6.5% over 30 years, you pay about $408,000 in interest alone — more than the house's down payment. Compare two scenarios side by side: a slightly lower rate or a shorter term usually saves more over 30 years than negotiating a few thousand dollars off the price. Remember that property taxes and insurance tend to rise over time, so budget with a cushion.

Common mistakes to avoid

The biggest error is quoting the rate as the monthly rate — always divide the APR by 12 in the payment formula. Second, forget the down payment: the loan principal is the home price minus the down payment, not the full price. Third, ignore PMI: with a down payment under 20%, PMI adds roughly 0.3–1.5% of the loan balance per year to the payment until you reach 20% equity. Finally, don't compare 15- and 30-year loans on the monthly payment alone — the 15-year's lower rate and half the interest term usually make it cheaper overall if you can afford the payment.

Tips for best results

Get pre-approved before house hunting so you know your real budget, and use the calculator with the actual rate quote rather than an estimate. Include all four PITI components — taxes, insurance, and HOA dues are often the difference between affordable and stretched. If you plan to stay more than 5–7 years, prefer a lower rate over a lower payment; if you plan to move sooner, a lower payment with a higher rate may win. Re-run the numbers after any big life change — refinancing can cut both the payment and the term when rates drop.

Authoritative source: Consumer Financial Protection Bureau