How this calculator works
The baseline payment clears the mortgage over your remaining amortization. Extra cash is added to every month-end payment, and the last payment is reduced to the remaining amount due. Canada mode uses nominal semi-annual compounding; US mode uses monthly compounding. The estimate assumes an unchanged rate and no penalties, fees or prepayment limits.
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
With $200,000 outstanding at 5% over 240 months in Canada mode, the base payment is $1,314.25. Adding $200 monthly clears the debt in 192 months, with a $261.18 final payment, and saves $25,937.07 in interest.
Frequently asked questions
Can I make unlimited extra payments?
Canadian mortgage agreements commonly restrict prepayments or charge penalties. Check your contract before using the estimated extra amount.
Is the last payment always a full payment?
No. It is capped at the remaining principal plus that month's interest. A zero opening balance needs no payments.
Does this include future rate renewals?
No. The rate stays fixed for the full calculation, even if your current mortgage term ends sooner.