How it works
Estimate the monthly payment, total interest and payoff time for a fixed-rate mortgage — with an optional down payment and extra payments.
Choose whether you know the loan amount or want to start from the property price. In price mode the calculator subtracts your down payment (amount or percent) to get the amount financed. It then applies the standard amortization formula and simulates every month, splitting each payment into interest and principal. Extra monthly or one-time payments shorten the schedule; the yearly amortization table and the interest saved both come from that same simulation. Property taxes, insurance and fees are not included unless you model them separately.
Formula
M = P × r × (1 + r)^n ÷ ((1 + r)^n − 1), where r = annual rate ÷ 12 and n = years × 12. With extra payments the schedule is simulated month by month.
P- Amount financed (price − down payment) (currency)
r- Monthly interest rate (annual % ÷ 12)
n- Number of monthly payments (months)
extra- Optional extra monthly or one-time payments (currency)
Examples
- 300,000 at 6% over 30 yearsLoan amount 300,000 · rate 6% · term 30 yearsMonthly payment ≈ 1,798.65 · total interest ≈ 347,514.57 · total repaid ≈ 647,514.57
- 375,000 home with 20% down at 6%Price 375,000 · down payment 20% · rate 6% · term 30 yearsAmount financed 300,000 · monthly payment ≈ 1,798.65
Frequently asked questions
Does the payment include taxes and insurance?
No. The calculator covers principal and interest only. Property taxes, homeowners insurance, mortgage insurance and fees are excluded unless you add them yourself.
What happens at 0% interest?
At 0% the payment is the amount financed divided by the number of payments, and total interest is 0.
How do extra payments work?
Extra monthly payments reduce the balance every month; a one-time extra payment is applied to the first payment. Both shorten the term and reduce total interest, and the table plus the interest-saved figure show the effect.
Can I use a term other than 15 or 30 years?
Yes — any whole number of years from 1 to 50 works, and the payment adjusts accordingly.
Are these results a lender quote?
No. They are estimates based on the numbers you enter and assume a fixed rate with equal payments.
How to read the result
The monthly payment stays fixed for the whole term. Early payments are mostly interest; later payments are mostly principal. A longer term lowers the payment but raises total interest, while extra payments do the opposite.
Limitations
Assumes a fixed interest rate, equal monthly payments and no fees, escrow, insurance or prepayment penalties. Actual lender offers can differ.
Source: Standard fixed-rate amortization formula (equal-payment loan); extra payments use an exact month-by-month simulation.