Mortgage Calculator
Calculate monthly P&I, total interest, and full amortization with optional tax, insurance, PMI, and HOA.
Written by Golam Rabbani, Founder & Lead Engineer — Last updated 2026-05-01
How to use this mortgage calculator
- Enter the home price and your planned down payment (toggle between $ amount and % of price); results update live as you type.
- Set the loan term in years — use the 30/20/15/10-year preset chips or type your own — and the annual interest rate (APR).
- Optionally add property tax, home insurance, PMI, and monthly HOA fees for a full PITI estimate, plus any extra monthly principal or a biweekly schedule to see interest saved and an earlier payoff date.
- Read the breakdown donut and the balance-vs-interest chart, and switch the amortization table between Annual and Monthly views (rows are dated, e.g. "Jun 2026").
- Use Copy for a text summary, Download CSV to export the schedule, or Print for a hard copy.
About this mortgage calculator
A mortgage calculator turns four numbers — home price, down payment, term, and interest rate — into a monthly principal-and-interest payment, plus the total interest you will pay over the life of the loan. This tool also lets you add property tax, home insurance, PMI, and HOA so you see a realistic monthly housing cost (commonly called PITI). It builds a full amortization schedule so you can see how much of each payment goes to interest versus principal in any month.
The math is the standard amortization formula: M = P × [r(1+r)^n] / [(1+r)^n − 1], where M is the monthly payment, P is the loan amount (price − down payment), r is the monthly interest rate (APR ÷ 12), and n is the total number of monthly payments (years × 12). For a $400,000 home with $80,000 down (20%), a 30-year term, and a 6.5% APR, the loan is $320,000, monthly r ≈ 0.005417, and n = 360, which gives a P&I payment of about $2,022.62 and total interest of about $408,142.36 over the life of the loan (a payoff roughly 30 years out). This is the same formula published by the U.S. Consumer Financial Protection Bureau (CFPB), see consumerfinance.gov/owning-a-home.
This calculator is for estimation only and is not financial advice — consult a qualified financial advisor or licensed mortgage broker before making a home purchase decision.
FAQ
- What does "P&I" mean and how is it different from PITI?
- P&I is principal and interest — the core mortgage payment. PITI adds property tax (T) and insurance (I) which are often escrowed. This calculator shows both: the P&I figure and a total-monthly that includes tax, insurance, PMI, and HOA when you enter them.
- How does the amortization schedule work?
- Each month the lender charges interest on your remaining balance (balance × monthly rate). The rest of your payment reduces the principal. Early in a 30-year loan most of each payment is interest; later payments are mostly principal. The schedule shows month, payment, interest, principal, and remaining balance.
- What is PMI and when do I need it?
- PMI (private mortgage insurance) is typically required when your down payment is less than 20% of the home price. Lenders usually quote it as 0.3–1.5% of the loan annually. Enter the annual figure and the tool will spread it across 12 months.
- Why does the total interest seem so high?
- A long-term loan accrues interest monthly on a slowly shrinking balance. Over 30 years at 6–7%, lifetime interest can rival or exceed the original loan amount. Making extra principal payments, choosing a shorter term, or refinancing when rates drop are the standard ways to reduce it.
- How do extra payments and the biweekly option work?
- Enter an extra monthly principal amount and the tool re-amortizes the loan, showing the interest you save and your new, earlier payoff date. The biweekly checkbox models the common "26 half-payments a year" strategy as roughly one extra monthly payment per year. Both apply only to principal, so they shorten the term without changing your scheduled payment.
- Does this tool send my numbers anywhere?
- No. The calculator runs entirely in your browser. Your inputs are never sent to a server, logged, or stored — refreshing the page clears everything.
- Should I use this for a final mortgage decision?
- No — use it for estimation only. Your actual rate, points, fees, escrow, taxes, and insurance will depend on your lender, location, credit profile, and the property. Always confirm the final figures with your lender before signing anything.