Auto Loan Refinance Calculator – Will Refinancing Save Money?

If your credit score has improved since you bought your car, or interest rates have dropped, refinancing could lower your payment and the interest you pay. But a lower rate doesn’t always mean you save. Fees, and especially a longer term, can wipe out the benefit. This calculator compares your current loan with a refinance offer and shows the net savings after fees.

How to use the auto loan refinance calculator

Enter your current loan balance, current APR and the months left on the loan.
Enter the new APR and new term from the refinance offer.
Enter any refinance fees you’ll pay upfront.

The results show the net savings, the current and new monthly payments, the change in payment, the total interest on each loan, and how many months the payment saving takes to pay back the fees.

How the savings are calculated

Both loans are amortized on the same balance:

payment = balance × r ÷ (1 − (1 + r)^−n)
interest = payment × n − balance
net savings = current interest − new interest − fees
break-even = fees ÷ monthly payment saving

The current loan uses your remaining months, and the new loan uses the new term. Comparing total interest, not just the payments, is what reveals whether a refinance really saves money.

Worked example

You owe $20,000 at 8.9% with 48 months left, and you’re offered 5.9% for 48 months, with $300 in fees.

Current payment: $496.75, with $3,844.08 of interest left to pay.
New payment: $468.78, which is $27.97 lower, with $2,501.64 of interest.
Net savings after fees: 3,844.08 − 2,501.64 − 300 = $1,042.44.
The fees are paid back by the lower payment after 11 months.

The trap: if you take 72 months at the same 5.9%, the payment falls to $330.51, but the interest rises to $3,797.04. After fees, you would be $252.96 worse off, even with a much lower rate.

Tips for refinancing a car loan

Keep the same term or shorter. That is how the lower rate turns into real savings.
Check your credit first. Refinancing makes sense when your score has improved enough to qualify for a noticeably better rate.
Compare several lenders, including credit unions, within a short window to limit the effect on your credit.
Check the car’s value. Lenders may decline if you owe more than the car is worth, or if the car is too old or has very high mileage.
Consider paying extra instead. If you can’t get a much better rate, extra payments may save more. Compare with the auto loan payoff calculator.

Common mistakes

Focusing on the monthly payment. A lower payment from a longer term often costs more overall.
Forgetting fees and prepayment penalties. Even small fees can cancel out a small rate cut.
Refinancing near the end of a loan. With only a few months left, most of the interest is already paid.
Rolling other costs into the new loan. Adding warranties or other debt to the refinance raises the balance and the interest.

Frequently asked questions

When does refinancing a car loan make sense?

Refinancing usually pays off when you can get a rate at least 1–2 points lower, you have more than a year or two left on the loan, and the fees are small. It is most common after your credit score has improved or market rates have fallen.

Can refinancing cost me more even with a lower rate?

Yes, if you stretch the term. Refinancing a $20,000 balance from 8.9% over 48 months to 5.9% over 72 months lowers the payment from $496.75 to $330.51, but the total interest rises, so you lose about $253 after fees.

Does refinancing hurt my credit score?

The lender's hard credit check may lower your score by a few points for a short time. Shopping for rates within a short window, usually 14–45 days, is typically counted as a single inquiry.

What fees come with refinancing a car loan?

Common costs are a lender origination fee (often zero for auto loans), a state title transfer or lien recording fee, and sometimes a prepayment penalty on the old loan. Add them all to the fees box.

Last updated October 31, 2026 · By the ZTool team