How to use the mortgage calculator
- Enter the home price — Type the purchase price of the home in dollars. This is the agreed sale price before any down payment is subtracted.
- Set your down payment — Enter the cash you'll put down up front, as a dollar amount. The calculator subtracts this from the price to find the amount you actually borrow.
- Add the rate and term — Enter the annual interest rate (APR) and the loan term in years, such as 30 or 15. These drive both the monthly payment and the total interest over the life of the loan.
- Read the results — The calculator shows your monthly principal and interest, the total interest you'll pay, and the total amount repaid. Adjust any input to compare scenarios side by side.
What this calculator shows
This tool estimates your monthly principal and interest (P&I): the part of your payment that goes toward repaying the loan plus the interest the lender charges. It also adds up the total interest and the total amount you'll pay over the full term, so you can see the true long-run cost of borrowing.
Keep in mind this is principal and interest only. Your real monthly housing cost is usually higher, because it also includes property taxes, homeowners insurance, and (where applicable) HOA dues or mortgage insurance. Treat the figures here as an educational estimate of the loan itself, not your full housing bill.
How the loan amount is set
The amount you borrow is simply the home price minus your down payment. If a home costs $350,000 and you put down $50,000, you finance $300,000. Everything else in the calculation builds on that loan amount.
A larger down payment lowers the loan amount, which lowers both the monthly payment and the total interest. It can also help you avoid mortgage insurance, which lenders often require when the down payment is small.
How rate and term swing the payment
The interest rate has a powerful effect on both your monthly payment and the interest you pay over time. On a $300,000 30-year loan, the monthly principal and interest is $1,610.46 at 5%, $1,798.65 at 6%, and $1,995.91 at 7% — so a one-point move in the rate shifts the payment by roughly $185 to $200 a month.
The term works differently. A longer term, like 30 years, spreads payments out so each month costs less, but you pay far more interest in total. A shorter term raises the monthly payment but cuts lifetime interest sharply. The table below shows how the loan amount alone moves the numbers at a fixed 6% APR over 30 years.
What can I afford?
A monthly payment that fits your budget is not the same as a payment a lender will approve. Lenders typically look at your total monthly housing cost — principal, interest, taxes, and insurance — as a share of your gross income, and many use guideline ratios such as keeping housing around 28% of income and total debt under about 36%.
Because of that, it's wise to budget using your full housing cost rather than P&I alone, and to leave room for maintenance and emergencies. The estimates here are for education and planning, not personalised financial advice — confirm the numbers with a lender before you commit.
How the monthly payment is calculated
M = P · r / (1 − (1 + r)^(−n)) (P = loan amount, r = monthly rate, n = months)
M is the monthly principal and interest payment.
P is the loan amount — the home price minus your down payment.
r is the monthly interest rate: the annual rate divided by 12 (so 6% APR becomes 0.06 / 12 = 0.005).
n is the total number of monthly payments — the term in years times 12 (a 30-year loan is 360 payments).
Total interest is the sum of all payments (M × n) minus the original loan amount P.
| Loan amount | Monthly (P&I) | Total interest | Total paid |
|---|---|---|---|
| $200,000 | $1,199.10 | $231,676 | $431,676 |
| $250,000 | $1,498.88 | $289,595 | $539,595 |
| $300,000 | $1,798.65 | $347,515 | $647,515 |
| $350,000 | $2,098.43 | $405,434 | $755,434 |
| $400,000 | $2,398.20 | $463,353 | $863,353 |