Mortgage Calculator
Enter a home price, down payment, term and interest rate to see your monthly mortgage payment broken into principal, interest, taxes, insurance and HOA — with total interest, total cost, and how an extra monthly payment pays the loan off sooner. Runs locally in your browser.
About this tool
Estimate a fixed-rate mortgage payment from the home price, down payment, loan term, and interest rate. The calculator breaks the monthly payment into principal and interest, property tax, insurance, and HOA dues, then totals the interest and ownership costs over the payoff period.
Worked example: a 400000 home with an 80000 down payment leaves a 320000
loan. At 6.5% over 30 years, the principal-and-interest payment is about
2022.62 per month before taxes, insurance, or HOA. Add annual tax,
homeowner's insurance, and HOA fields to estimate a fuller PITI-style monthly
housing payment.
Use extra_monthly_payment to model additional principal payments. The base
monthly payment stays the scheduled mortgage payment, while the amortization
loop applies the extra amount each month to calculate fewer payoff months and
lower total interest.
Limits and edge cases: this is a deterministic fixed-rate calculator, not loan advice. It does not include PMI, closing costs, adjustable-rate resets, escrow rules, tax deductions, late fees, biweekly schedules, or lender-specific rounding. Enter taxes and insurance as annual amounts; enter HOA as a monthly amount. The down payment is a currency amount, not a percent.
FAQ
What does the monthly payment include?
monthly_payment includes scheduled principal and interest plus monthly taxes,
insurance, and HOA dues. It does not include the optional
extra_monthly_payment; that amount is applied separately to shorten the loan.
Is the down payment a percent?
No. Enter the down payment as a currency amount. For a 20% down payment on a
400000 home, enter 80000.
How are taxes and insurance handled?
Enter property tax and homeowner's insurance as annual amounts. The calculator divides each by 12 and includes those monthly amounts in the payment and the payoff-period totals.
How does an extra monthly payment affect the result?
The extra payment is applied directly to principal in the amortization loop.
That can reduce payoff_months and total_interest; the reported scheduled
principal-and-interest payment stays unchanged.
Developer & Automation Access
Run it from the terminal
Same engine as this page, headless — via the gizza CLI:
gizza tool mortgage-calculator 'home_price=400000'New to the CLI? Get gizza →
Open it by URL
Pre-fill and auto-run this tool with query parameters — the names match the API/CLI:
https://gizza.ai/tools/mortgage-calculator/?home_price=400000&down_payment=80000&loan_years=30&annual_interest_rate_percent=6.5&annual_property_tax=4800&annual_insurance=1800&monthly_hoa=0&extra_monthly_payment=0&decimals=2Machine-readable descriptor: tool.json — title + parameters JSON Schema for agents.