Mortgage Payoff Calculator
See how much sooner, and how much cheaper, an extra payment or lump sum can get you to a paid-off mortgage.
How the calculation works
Works from your loan balance today, whether that's a brand-new loan or one you're partway through, not the original loan amount from years ago. First it finds your standard required monthly payment for that balance, rate, and remaining term. A one-time lump sum, if you enter one, comes off the balance immediately. Then it simulates paying that reduced balance with your extra monthly amount added to every payment: interest still accrues on whatever balance remains, but the balance falls faster, so it reaches zero in fewer months. The difference in months and in total interest between that accelerated schedule and the original one is what the extra payment and lump sum save you together.
Formula
Standard Payment comes from the usual amortization formula on your loan balance, rate, and remaining term. A lump sum reduces the starting balance immediately; adding the extra monthly amount to the standard payment and simulating the balance to zero from there gives a shorter payoff time and less total interest than the original schedule.
Examples
$320,000 balance, 6.5% rate, 30-year remaining term, $200 extra/month
Payoff in 281 months instead of 360 (79 months sooner), $105,428.67 interest saved
$280,000 balance, 6.75% rate, 22-year remaining term, $300 extra/month + $10,000 lump sum
Payoff in 187 months instead of 264 (77 months sooner), $91,218.94 interest saved