How to use the mortgage calculator
- Enter the loan amount, annual interest rate and term in years.
- Add a down payment if you have one — it's subtracted from the loan.
- See your monthly payment plus the total interest and total amount paid over the life of the loan.
How the monthly payment is calculated
It uses the standard amortizing-loan formula: M = P · r(1+r)ⁿ ⁄ ((1+r)ⁿ − 1), where P is the loan amount, r is the monthly interest rate (annual rate ÷ 12), and n is the number of monthly payments (years × 12). Early payments are mostly interest and later ones mostly principal, but the monthly amount stays the same. This covers principal and interest only — property tax, insurance and HOA fees are extra.
Benefits
- Shows your monthly principal-and-interest payment instantly.
- Breaks down total interest and total amount paid over the loan.
- Handles a down payment and any rate or term.
- Private — nothing is uploaded.
Limitations to know
- It covers principal and interest only — not property tax, insurance or HOA fees.
- It assumes a fixed rate for the whole term.
- It does not model extra payments or bi-weekly schedules.
Common mistakes to avoid
- Forgetting to budget for taxes and insurance on top of this payment.
- Comparing loans by monthly payment alone instead of total interest.
- Entering the rate as a decimal instead of a percent (use 6.5, not 0.065).
Alternatives
For non-home loans use the Loan Calculator; to work out a deposit as a percentage use the Percentage Calculator.
Last updated: August 2026 · Reviewed by the AI Toolbox editorial team.
Frequently asked questions
Does it include taxes and insurance?
No — it shows principal and interest. Add property tax, home insurance and any HOA fees separately for a full monthly cost.
How does a bigger down payment help?
It reduces the loan amount, which lowers both your monthly payment and total interest.
What if the rate is 0%?
The payment is simply the loan amount divided by the number of months.
Is my data saved?
No — everything is calculated in your browser.