About this calculator
A mortgage is almost always the largest loan most people ever take on, so a small difference in interest rate or loan term can mean tens of thousands over the life of the loan. This calculator turns the standard amortization formula lenders use into a plain-English estimate: enter your home price, down payment, interest rate, and loan term, and it works out your monthly principal-and-interest payment, the total interest you'll pay, and the total amount you'll hand over by the time the loan is paid off. It's the same math a bank's loan officer would run, just without the sales pitch. The calculator works in any currency — pick the symbol that matches your own before you start typing numbers.
How it works
The calculator uses the standard fixed-rate amortization formula: M = P × [r(1+r)^n] / [(1+r)^n − 1], where P is the loan principal (home price minus down payment), r is the monthly interest rate (your annual rate divided by 12), and n is the total number of monthly payments (loan term in years × 12). This is the formula used by virtually every fixed-rate mortgage lender, so the payment figure you get here should closely match a lender's quote for the same rate and term — though your actual bill will also include property taxes, homeowners insurance, and possibly PMI or HOA fees, which this tool doesn't include since they vary so much by location.
Worked example
Say you're buying a $350,000 home with a $70,000 down payment (20%), leaving a $280,000 loan, at a 6.5% annual rate over 30 years. Plug those into the calculator above and you'll get a monthly principal-and-interest payment of about $1,769.79. Over 360 payments that's roughly $636,924 paid in total, of which about $356,924 is interest — more than the original loan amount, which is exactly why even a half-point difference in rate is worth shopping around for.
Formula cross-checked against: Consumer Financial Protection Bureau — Explore Interest Rates.
Frequently asked questions
Does this include property tax and insurance?
No. This calculator estimates principal and interest only, since taxes, insurance, PMI, and HOA dues vary widely by location and lender. Many mortgage statements bundle those into an escrow payment on top of the number shown here.
What's a realistic interest rate to enter?
Use the rate a lender has actually quoted you, or a current national average rate for your loan term and credit profile — rates change often, so a quote from the last few weeks will be far more accurate than a rate you remember from a year ago.
How much difference does the loan term make?
A shorter term (like 15 years instead of 30) usually comes with a lower interest rate and dramatically less total interest, but a noticeably higher monthly payment — try both terms here to see the trade-off in real numbers.
Last reviewed: September 2026.