Paying extra on a car loan: how much interest and time you save
A small extra payment each month can take months off a car loan and save hundreds or thousands in interest. Here's the math on a $25,000 loan, including rounding up, lump sums and biweekly payments, and how to make sure it counts.
By the LotGauge team
Extra principal shortens the loan and cuts interest
Most auto loans charge simple interest on the remaining balance. Any extra amount you pay toward principal lowers that balance immediately, so every later payment carries less interest and more of it goes to principal. The result is an earlier payoff and less total interest.
What different extra amounts save
Take a $25,000 loan at 7% APR over 72 months. The scheduled payment is $426.23 and total interest is about $5,688.
+$50 a month: paid off in 63 months (9 months early), about $4,935 interest, saving roughly $750. +$100 a month: 56 months (16 early), about $4,361 interest, saving roughly $1,330. +$200 a month: 46 months (26 early), about $3,543 interest, saving roughly $2,150. Open the +$100 example in the calculator.
Other ways to pay extra, worked out
Same loan: $25,000 at 7% for 72 months, $426.23 a month.
Round up to $450. An extra $23.77 a month pays the loan off in 68 months, 4 early, and saves about $385.
One lump sum. Put a $1,000 tax refund toward principal in month 6 and the loan ends 3 months early, saving about $457. Do it once a year for three years ($3,000 total) and you finish 9 months early and save about $1,013. Money paid early saves more than the same money paid late, because it stops interest for longer.
Half payments every two weeks. Paying half the bill every two weeks adds up to 26 half payments a year, one extra full payment. That's like adding about $35.52 a month: 66 months instead of 72, saving about $557. It only works if your lender applies each half payment when it arrives. Many hold a half payment until the second one comes in, so ask first, or just add the extra to your monthly payment instead.
The higher your rate, the more it saves
Extra payments are worth more on an expensive loan. The same $25,000 over 72 months at 13.93% APR (Experian's Q2 2026 average used-car rate for fair credit, 601–660) costs $514.21 a month and about $12,023 in interest. An extra $100 a month ends it in 56 months and saves about $2,985, more than twice what it saves at 7%. See how APR and credit score change the payment, and if your credit has improved since you bought, refinancing may save more than extra payments.
Make sure the extra goes to principal
Some lenders treat extra money as an early payment of next month's bill rather than a principal reduction. Ask your lender how to mark a payment "principal only," and check your statement afterward. Also check your contract for prepayment penalties; they're uncommon on auto loans but not unheard of.
When extra payments may not be the best move
If you carry higher-interest debt such as credit cards, or don't have an emergency fund, those usually come first. If your auto loan rate is very low, the guaranteed "return" from paying it down early is small. The right choice depends on your rate and your other goals.
Model it
Enter your loan in the car payment calculator and set "Extra principal / month" to see the months saved, interest saved and the full amortization schedule. For loan-length trade-offs, see 72 vs. 84 month car loans.
Sources
Experian, average used-car loan rates by credit score (Q2 2026). Payoff months and interest were calculated with LotGauge's loan math, assuming every payment is made on time and extra money goes to principal; your lender's figures may differ slightly.