PFCHow to use this calculator
A mortgage payment usually includes both interest and principal. This calculator shows how that split changes over the life of a fixed-rate loan and what happens when you pay additional principal each month.
- Enter the loan amount and contract interest rate.
- Choose the loan term and, if applicable, an extra monthly principal payment.
- Calculate to compare total interest, payoff time, and the detailed payment schedule.
Illustrative example
For a $250,000.00 loan over 30 years at 6.5%, the monthly principal-and-interest payment is $1,580.17. With no extra payments, total modeled interest is $318,861.58.
These example values are for explanation. They are not current market quotes or personalized recommendations.
Calculation method
The scheduled payment is P × r ÷ [1 − (1 + r)^(−n)], where P is the loan amount, r is the annual rate divided by 12, and n is the number of monthly payments. At a zero interest rate, the payment is P ÷ n. Interest and payments are rounded to cents each month.
Assumptions and limitations
Monthly principal and interest, rounded to cents. Excludes taxes, insurance, fees, and penalties; the last installment absorbs rounding. Extra principal is paid every month. For an ARM, the first reset is after the fixed period; each reset uses the projected index plus margin, subject to symmetric adjustment caps, a lifetime upper cap, and a floor. Payments are recalculated over the remaining term. Extra-payment savings use the same rate scenario with no extra payments. This is a scenario, not a prediction; lender-specific rounding, lookback rules, interest-only periods, and payment caps are not modeled.
Sources
Mortgage amortization calculator FAQs
Choose a question to read the answer, then try your own numbers in the free calculator.
What is mortgage amortization?
Mortgage amortization is the gradual repayment of a home loan through scheduled payments of principal and interest. On a standard fixed-rate, fully amortizing loan, the principal-and-interest payment stays level, while the interest share generally falls and the principal share rises as the balance is paid down.
How is a mortgage payment calculated?
The payment depends on the loan balance, monthly interest rate, and number of payments. The calculator spreads principal and interest across the selected term, then builds a month-by-month schedule. Use the contract interest rate rather than an APR that includes loan fees.
Does this include escrow?
No. This calculator shows principal and interest. Taxes, homeowners insurance, HOA fees, mortgage insurance, and other charges can increase the amount you pay each month.
How do extra payments help?
After interest is covered, additional payments reduce the balance. The calculator compares your result with the same loan without extra principal payments.
Why is the final payment different?
Rounding payments and interest to cents can leave a small remainder. The final installment settles the remaining principal and interest.
PFC provides mathematical planning estimates. Tax and retirement rules in these tools are for 2026 and do not update automatically. Check the cited sources and the terms that apply to your situation.