How the math works
Standard amortization
Every calculator here uses the same monthly amortization model lenders use. Each month your balance grows by one month of interest (your annual rate divided by twelve), then your payment is subtracted. Whatever is left carries into the next month.
Payment from a term
When you tell us how many years are left, we solve for the level payment that clears the balance exactly on schedule: P × i ÷ (1 − (1 + i)⁻ⁿ), where i is the monthly rate and n is the number of months.
Payoff time from a payment
When you tell us the payment instead, we solve the same equation for months. If your payment is smaller than one month of interest, the balance grows forever — we'll say so rather than show a number.
What isn't included
Results exclude escrow, property taxes, insurance, PMI, late fees, and any prepayment penalties in your contract. Variable-rate debt is modeled at the rate you enter. Treat everything here as a planning estimate and confirm exact payoff figures with your lender.