A mortgage calculator is the fastest way to answer the most important question in home buying: what will this actually cost me every month? Instead of guessing from the sticker price, this free tool turns the loan amount, interest rate, and term into a precise monthly payment figure — plus the total interest you will pay over the life of the loan.
Most buyers are surprised by how much the interest rate matters. On a $240,000 loan, the difference between a 6% and a 7% rate is roughly $150 every single month — more than $50,000 across a 30-year term. Running the numbers before you talk to a lender puts you in a far stronger negotiating position, because you already know what payment fits your budget.
Our calculator uses the standard amortization formula lenders use: the monthly payment covers interest first, then principal, with the balance shrinking a little more each month. Taxes, insurance, and HOA dues are not included, so treat the result as your principal & interest payment and add those costs on top for the full picture.
How to use the Mortgage Calculator
- Enter the home price (or the loan amount if you already know it) in dollars.
- Add your down payment. The calculator subtracts it automatically — a bigger down payment means a smaller loan and less interest.
- Set the annual interest rate from your lender quote, e.g. 6.5.
- Choose the loan term (15 or 30 years are most common) and click Calculate payment.
- Compare scenarios: change the rate or term and recalculate to see how each choice affects your monthly budget and lifetime cost.
Tips for accurate results
- A 15-year term roughly doubles the monthly payment but can save you hundreds of thousands in interest.
- Even a 0.5% lower rate is worth shopping for — get at least three lender quotes.
- Remember to budget property tax, homeowner's insurance, and PMI (if your down payment is under 20%) on top of this figure.
- Making one extra payment per year can shave years off a 30-year loan.
What affects your mortgage payment?
Three inputs drive everything: the loan amount (price minus down payment), the interest rate, and the term. A larger down payment does double duty — it shrinks the loan and can eliminate private mortgage insurance. Shorter terms mean higher monthly payments but dramatically lower total interest, which is why 15-year loans are popular with buyers who can afford the payment.
Frequently asked questions
How is the monthly mortgage payment calculated?
Lenders use the amortization formula M = P·r(1+r)ⁿ / ((1+r)ⁿ−1), where P is the loan amount, r the monthly interest rate, and n the number of payments. Our calculator applies exactly this formula.
Does this include property taxes and insurance?
No — the result is principal and interest only. Add your estimated monthly property tax, homeowner's insurance, HOA fees, and PMI (if applicable) for the complete monthly housing cost.
Is a 15-year or 30-year mortgage better?
A 15-year loan has higher payments but far less total interest and builds equity faster. A 30-year loan has lower payments and more flexibility. The right choice depends on your income stability and other financial goals.
Can I trust an online mortgage estimate?
For principal and interest, yes — the math is standardized. Your lender's final offer may differ slightly due to fees, points, and the exact day the rate locks, but this estimate will be very close.