Extra Loan Payment Calculator
An extra loan payment calculator shows what happens when you add a fixed amount to the principal every month. You type the rate. The result is a payoff time and the interest saved, not a tax estimate.
You type the rate. This page does not look one up.
Payoff time
3 years 11 months
Interest paid
$2,444.36
Interest saved
$754.99
Months saved
13
Formula
The base loan is a normal fixed payment. The extra amount is applied to principal on top of that payment. Interest each month is calculated on the remaining balance, then rounded to the cent the way a lender statement does. The last payment is only what is still owed, even if that is smaller than the usual payment plus the extra.
Paying extra does not change the interest rate. It shortens the number of months and cuts the interest that would have been charged on the balance you paid off early. The comparison on this page is against the same loan with no extra payment.
The figure is a planning estimate. A lender may apply extra payments differently, require a note that the extra is for principal, or charge a prepayment fee. Those rules are not modeled here. Taxes and insurance are not included.
If the extra amount is larger than the remaining balance, the schedule stops. You will not see a payment that overpays the loan. Enter 0 in the extra field to see the original term. A modest extra payment can remove several payments at the end of the schedule, which is where much of the remaining interest would have been charged.
Each month: interest = balance × r, then principal = payment + extra − interest
- r Monthly interest rate, the annual rate divided by 12.
- payment The scheduled monthly payment of the original loan, rounded to the cent.
- extra Additional principal paid every month, until the final payment.
Worked example
The same $20,000 loan at 6% for 5 years, with an extra $100 sent to principal every month.
The loan is paid off in 3 years 11 months, which is 13 months sooner. Interest saved is $754.99.
The last payment is only the remaining balance. It is not a full installment plus the extra $100.
FAQ
Does the extra payment reduce interest?
Yes, when the rate is above zero. The extra amount reduces the balance, so later months charge interest on less principal.
What if the last extra payment is larger than the balance?
The last payment is capped at the remaining balance plus that month’s interest. The schedule does not collect more than you owe.
Is this the same as a biweekly payment?
No. This page adds one extra amount once a month. It does not model a payment every two weeks.
Will my lender apply the extra this way?
Many do if you mark the extra as principal. Some apply it to the next payment instead. Check the loan terms before you rely on the months saved.