How this calculator works
Start with the current mortgage balance and the amortization it would have without extra payments. The calculator finds the regular payment, adds your extra amount each month and solves for the first month that clears the debt. It reduces the final payment as needed. Canada mode compounds semi-annually and US mode compounds monthly; both pay monthly.
Formula
i = (1 + r/2)^(1/6) - 1 in Canada, or r/12 in US mode. Base payment A = P × i / (1 - (1 + i)^(-N)), or P/N at 0%. Each month: due = balance × (1 + i); payment = min(A + extra, due); new balance = due - payment. Interest saved = N × A - total paid.
Worked example
At 0%, a $1,200 balance over 12 months has a $100 baseline payment. Paying an extra $25 monthly clears it in 10 months: nine payments of $125 and a final payment of $75. Interest and interest saved are both $0.
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Frequently asked questions
What if I make no extra payment?
Payoff takes the original number of months and interest saved is $0, assuming the rate and payment schedule remain unchanged.
Does this give an exact calendar payoff date?
It reports monthly payment periods. Actual calendar dates, daily interest, cent rounding and future renewals can change a lender's payoff quote.
Are prepayment penalties included?
No. Check the permitted prepayment amount and any penalty in your mortgage agreement before acting on the estimate.