What an extra payment actually does to your loan

Straight to principal, on top of your regular payment. Because interest is calculated on the remaining balance each month, reducing that balance faster means less interest accrues for the rest of the loan — which compounds into real savings.

Not necessarily — it depends on your rate versus what you could earn investing that money elsewhere, and whether you have higher-interest debt to pay down first. This calculator shows you the mechanical effect on the loan; it's one input to that decision, not the whole answer.

Because payoff isn't linear — the balance drops slowly at first and rapidly near the end. Seeing it year by year makes clear roughly when extra payments start making the biggest difference.