How much money does paying extra on a personal loan actually save?

The math of extra payments: Interest accrues daily on your outstanding principal. Every dollar of principal you pay off stops accruing interest immediately. The savings compound: paying down the principal sooner also means subsequent minimum payments include less interest and more principal, creating a cascade of earlier payoff.

Example calculation: $12,000 personal loan at 15% APR over 48 months. Standard payment: $334/month. Total interest at standard pace: approximately $3,993.

Scenario A - One extra $500 payment in month 3: Saves approximately $430 in total interest. Payoff moves from month 48 to month 44 (4 months earlier). ROI on the $500 extra payment: 86% annualized interest savings rate.

Scenario B - Extra $50/month every month starting month 1: New total payment: $384/month. Saves approximately $930 in total interest. Payoff moves from month 48 to month 40 (8 months earlier).

Early vs late extra payments: Extra payments made early in the loan life save significantly more than the same payments made late. This is because early extra payments have more remaining months to compound their interest-avoidance effect. A $500 payment in month 1 saves roughly 2x as much interest as the same payment in month 30.

Instructions matter: When making an extra payment, specify 'apply to principal balance' explicitly. If you do not specify, the servicer may apply the extra amount to your next scheduled payment, which does not immediately reduce interest accrual. Most servicers allow you to specify principal application in their payment portal.