The mortgage payment calculator helps you estimate your monthly principal and interest payment based on your loan amount, interest rate, and loan term. Enter the amount you plan to borrow, the APR your lender quoted, and the length of the mortgage to see your monthly payment, total interest paid over the life of the loan, and a complete amortization schedule.
A fixed-rate mortgage uses an amortization formula that splits each monthly payment between interest (charged on the remaining balance) and principal (paid down on the loan). The payment amount stays the same every month, but the mix shifts: early payments are mostly interest, later payments are mostly principal.
P is the loan amount, r is the monthly interest rate (APR ÷ 12), and n is the total number of monthly payments (years × 12).
If you borrow $400,000 at a 6.75% APR for 30 years, your monthly principal and interest payment is about $2,594. Over the full 30 years you pay roughly $933,952 — meaning $533,952 of that is pure interest.
On a $400,000 loan at 6.75%, your very first payment is roughly $2,250 interest and only $344 principal. By year 15 the split flips. This is why selling a home in the first few years feels like you've barely dented the loan — because you have.
This calculator shows principal and interest only. Lenders also collect property taxes and homeowners insurance into an escrow account each month — together with PMI for low-down-payment loans, that bundle is called PITI. Plan on PITI being 20–30% higher than the P&I number here.
A fixed-rate mortgage locks the rate for the full term. An ARM (e.g. 5/1, 7/6) starts lower, then resets at intervals based on a market index. Fixed-rate is the right default unless you're confident you'll sell or refinance before the reset.
The interest rate alone determines your payment. The APR also bakes in lender fees, points, and most closing costs spread across the loan, so it's a more honest apples-to-apples number when comparing offers.
Across the full term, 57¢ of every dollar paid is interest — front-loaded into the early years.
It takes until year 20 for monthly principal to overtake monthly interest. Until then, you're mostly paying the bank.
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| Scenario | Inputs | Result | Note |
|---|---|---|---|
| $300K loan, 30-year fixed | Loan: $300,000 APR: 6.75% Term: 30 yrs | $1,946 | Total interest over 30 years: about $400,464. |
| $400K loan, 30-year fixed | Loan: $400,000 APR: 6.75% Term: 30 yrs | $2,594 | Total interest over 30 years: about $533,952. |
| $400K loan, 15-year fixed | Loan: $400,000 APR: 6.00% Term: 15 yrs | $3,375 | Total interest: about $207,577 — roughly $326K less than the same loan at 30 years. |
To see how extra principal payments would change these numbers, use our Loan Payoff Calculator.
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