Mortgage Payoff Calculator
See how extra payments shorten your mortgage and how much interest you save.
About the Mortgage Payoff Calculator
Enter what you still owe, your rate, the years left, and an extra amount you could add each month or as a one-off lump sum. The calculator keeps your regular payment the same and sends every extra amount to principal, then shows the new payoff date and the interest saved.
Because interest is charged on the remaining balance, each extra amount stops interest building on it for the rest of the loan. That's why small regular overpayments early in a mortgage save the most.
The formula
Each month: balance = balance × (1 + i) − (payment + extra)
- i
- monthly rate: yearly rate ÷ 12
- payment
- your regular monthly payment, which stays the same
- extra
- the additional amount you choose to pay
Worked example
$250,000 left at 6.5% with 25 years to go
- Regular payment: $1,688.02 a month
- With $200 extra a month: paid off in 19 years 6 months, 5 years 6 months sooner
- Interest saved: about $64,928
Things to keep in mind
- Assumes a fixed rate. For an adjustable-rate mortgage, re-run it when the rate changes.
- Property tax, insurance and fees held in escrow are not included.
- Check for prepayment penalties or overpayment limits in your contract.
Questions people ask
Should I overpay or invest?
Overpaying earns a guaranteed return equal to your mortgage rate. Investing may earn more, with risk; many people do some of each.
Are there limits?
Some lenders (common in the UK) cap overpayments, often at 10% of the balance a year without fees.
Does a lump sum or monthly extra save more?
Money paid sooner saves more. A lump sum now beats the same total spread over later years.