Mortgage Payoff CalculatorFree online financial calculator — instant results, no sign-up

m = B × [i(1 + i)^mo] / [(1 + i)^mo − 1]
m2 = m + extra
k = −ln(1 − (B × i / m2)) / ln(1 + i)
Interest saved = (m × mo) − (m2 × k)

• BCurrent remaining mortgage principal balance ($)
• iMonthly interest rate, calculated as annual interest rate / 1200
• moOriginal remaining term in months (Remaining term in years × 12)
• mStandard monthly principal and interest payment ($)
• m2Total monthly payment including extra contribution ($)
• kRecalculated total months required to pay off the remaining balance

First, standard monthly amortization is computed from the balance, annual rate, and remaining months. The extra monthly amount is added to establish the new payment, and the logarithmic number-of-periods formula calculates the shortened duration. Payoff time is displayed as whole years and rounded-up months, while total interest saved is computed by subtracting the new total payments from the original scheduled total payments.

These are the calculator's starting values and the results it actually produces for them.

1. 1Compute the standard baseline monthly payment using standard amortization across the remaining months.
2. 2Add the extra monthly amount to determine the accelerated monthly payment.
3. 3Solve for the new number of months required to reduce the loan balance to zero at the monthly interest rate.
4. 4Subtract the accelerated total payments from the baseline total payments to derive interest saved, and subtract accelerated months from baseline months to determine time saved.

Further reading

• CFPB: What is a prepayment penalty?