How this calculator works
Your regular payment is worked out from the balance, rate and remaining years. The extra amount is added each month and goes entirely to principal.
Because each month’s interest is charged on a smaller balance, the savings compound: a modest extra payment can remove years from the loan.
The calculator compares the remaining interest with and without the extra payment.
Check with your servicer that extra payments are applied to principal and that there is no prepayment penalty.
Worked example
$250,000 balance at 6.5% with 25 years left, plus $200 a month
- Regular payment: $1,688.02.
- With $200 extra, the loan ends about 5½ years sooner.
- Interest saved: tens of thousands of dollars compared with the regular schedule.
Questions people ask
Is it better to pay extra monthly or a lump sum?
Both reduce interest. A lump sum saves more the earlier it is paid; a monthly amount is easier to sustain. The savings depend on timing, not the method.
Will my monthly payment go down if I pay extra?
Usually not. The payment stays the same and the loan ends sooner, unless you ask the lender to recast the loan after a large lump sum.
Should I pay off my mortgage early?
It makes most sense if your rate is high and you already have emergency savings and are getting any employer retirement match.
Last reviewed October 2, 2026