Mortgage Calculator
Calculate your monthly mortgage payment, total interest, and total loan cost in seconds. Enter your home price, down payment, interest rate, and loan term — the calculator does the rest using the standard amortization formula. No sign-up, no credit check, no data sent to a server.
Quick answer
Monthly payment = P × [r(1+r)^n] / [(1+r)^n − 1], where P is the loan amount, r is the monthly interest rate, and n is the total number of monthly payments. This calculator shows principal and interest only — add 20–40% for taxes, insurance, and PMI.
Mortgage Calculator
How the mortgage calculator works
Under the hood, this calculator uses the standard amortization formula used by every bank
and mortgage servicer in the United States. Given a loan amount P, a monthly interest rate r,
and a total number of monthly payments n, the monthly payment M is calculated as
M = P × [r(1+r)^n] / [(1+r)^n − 1]. The loan amount is your home price minus
your down payment. The monthly rate is the annual rate divided by 12 and converted from a
percentage (so 6.5% becomes 0.00542). The number of payments is the loan term in years
multiplied by 12.
Total interest paid is the sum of all monthly payments minus the original loan amount. Total cost is the loan amount plus total interest — or equivalently, the monthly payment times the number of payments. For a $240,000 loan at 6.5% over 30 years, you'll pay about $1,517 per month, $306,027 in interest, and $546,027 total over the life of the loan.
When to use it
Use this calculator before house-hunting to figure out what you can realistically afford. Most lenders will approve you for a loan with a monthly payment up to 28% of your gross monthly income, but the "affordable" figure is typically lower once you factor in car payments, student loans, childcare, and savings goals. Run the math yourself before a lender tells you what you "qualify" for.
It's also the fastest way to compare loan options. Want to see what a quarter-point rate difference costs over 30 years? Run both. Wondering if a 15-year is worth the higher payment? Run both — the 15-year almost always saves six figures in interest. Curious what a bigger down payment does? Same idea. Every number here is directly comparable.
Common mistakes
- Forgetting taxes and insurance. This calculator shows P&I only. Your actual monthly housing cost (PITI) adds property taxes, homeowners insurance, and — if you put less than 20% down on a conventional loan — private mortgage insurance. In many markets that adds $300–$800 per month on top of the P&I shown here.
- Chasing a lower monthly payment at any cost. A 30-year loan has a lower payment than a 15-year loan because you're stretching the same interest over twice as many payments. The 30-year wins for cash flow; the 15-year wins for total cost. Neither is "right" — it depends on your goals.
- Ignoring the APR vs the interest rate. APR includes loan origination fees and points; the interest rate does not. When comparing lender quotes, always compare APR to APR, not rate to rate.
- Treating the pre-approval number as your budget. Banks approve based on debt-to-income ratio, which doesn't account for retirement savings, emergency funds, or discretionary spending. Set your own budget first, then see if the bank will approve it.
Frequently asked questions
How do I calculate a mortgage payment?
Use the standard amortization formula: M = P × [r(1+r)^n] / [(1+r)^n − 1]. P is the loan amount, r is the monthly interest rate (annual rate ÷ 12 ÷ 100), and n is the number of months (years × 12). Or just use the calculator above.
Does this mortgage calculator include taxes and insurance?
No. This calculator shows only principal and interest (P&I). Property taxes, homeowners insurance, and PMI typically add 20–40% on top of the P&I payment. Add those separately to estimate your full PITI payment.
Is a 15-year or 30-year mortgage better?
A 15-year mortgage has a much lower total interest cost but a higher monthly payment. A 30-year mortgage has a lower monthly payment but you pay far more interest over the life of the loan. Run both in the calculator to see the tradeoff for your specific numbers.
How much down payment do I need?
A 20% down payment avoids private mortgage insurance (PMI) on conventional loans. FHA loans allow as little as 3.5% down. VA and USDA loans can be 0% down for eligible borrowers. More down means a lower monthly payment and less total interest.
Why is my actual mortgage quote higher than the calculator?
Your quote likely includes escrowed taxes and insurance, PMI (if <20% down), and possibly HOA fees. The calculator here is just P&I — the base amount before those add-ons.