How extra payments help
Each month: interest = balance × monthly rate. The rest of the payment cuts principal. Extra money goes to principal. The loan ends when the balance hits zero. If the payment does not cover interest, the balance grows and this page will say so.
Confirm with your lender that extra amounts apply to principal and that there is no prepayment penalty.
Worked example
A $12,000 loan at 8% with a $240 minimum payment takes years to clear. An extra $50/month shortens the term and cuts total interest. The exact months depend on how the lender applies extra principal.
Some loans (especially car loans) have prepayment rules. A mortgage prepayment can be a lump sum against principal or an increased regular payment — this page models extra monthly principal.
Common questions
Should I include escrow?
No. Use principal and interest only.
Biweekly payments?
Treat them as a higher monthly extra, or run two weeks as half the monthly bill twice.