Mortgage Calculator
Most home buyers underestimate their real monthly cost by a few hundred dollars — not because the math is wrong, but because they forget property taxes and insurance stack on top of the loan payment itself. This calculator gives you the core principal-and-interest number that forms the base of that total.
Enter your loan details to see your monthly payment.
How to use this calculator
- Enter your loan amount (home price minus down payment).
- Enter your interest rate and loan term.
- Click "Calculate my payment" to see your principal and interest payment.
How the calculation works
This uses the standard amortization formula lenders use: Monthly P&I = Loan × [r(1+r)ⁿ] / [(1+r)ⁿ − 1], where r is your monthly interest rate (annual rate ÷ 12) and n is your total number of payments (years × 12). The result is a fixed monthly payment that stays level for the life of the loan, even though the split between principal and interest within that payment shifts — early payments lean heavily toward interest, later ones toward principal.
A worked example
Say you borrow $300,000 at 6.5% over 30 years. The formula produces a monthly principal-and-interest payment of about $1,896. Over all 360 payments, you'll pay back roughly $682,600 total — meaning about $382,600 of that, more than the original loan itself, is pure interest. Switch to a 15-year term at the same rate and the monthly payment rises to around $2,613, but total interest drops to roughly $170,300 — less than half — because the loan is paid off in half the time.
Frequently asked questions
Does this include property tax and insurance?
No — this calculates principal and interest (P&I) only. Your total monthly housing payment (PITI) will be higher once taxes, insurance, and any HOA fees are added.
Why does a longer term lower my payment but cost more overall?
Spreading the same loan over more months lowers each payment, but you pay interest for longer — resulting in more total interest paid over the life of the loan.
What rate should I use to estimate?
Use a current quote from a lender, or a recent average mortgage rate for your loan type as a starting estimate.
What is PMI and when do I need it?
Private Mortgage Insurance is typically required when your down payment is below 20% of the home's value, generally costing 0.5%-1.5% of the loan amount annually. It usually drops off once you reach 20% equity.
What does PITI stand for?
Principal, Interest, Taxes, and Insurance — the four components lenders combine to calculate your full monthly housing payment, used to determine what you qualify to borrow.