🚗 Car Loan Refinance Calculator
By Shihab Mia · Updated 2026-07-01
This calculator gives an estimate only. It assumes a fixed APR, standard monthly amortization and no fees, taxes or add-on products. Your real savings depend on your lender's exact terms, any refinance or title fees, prepayment penalties on the old loan and how your credit affects the rate you are offered. This is not financial advice, confirm the numbers with the lender and speak to a qualified adviser if you need help.
| Item | Current loan | Refinanced loan | Difference |
|---|
This car loan refinance calculator shows whether refinancing your auto loan is worth it by comparing your current loan to a new one side by side. Enter your remaining balance, current APR and the months left, then a new APR and term, and it works out both monthly payments, the total interest each way, your monthly savings and your lifetime interest savings. It also flags when a lower monthly payment comes from a longer term that could cost you more interest overall.
What is the Car Loan Refinance Calculator?
Refinancing a car loan means replacing your existing loan with a new one, ideally at a lower interest rate. The new loan pays off the old balance, and you make payments to the new lender instead. The two things that change your cost are the APR (annual percentage rate) and the term (how many months you spread the payments over). A lower APR always saves you money. A longer term lowers the monthly payment but can quietly raise the total interest, because you are borrowing the same money for longer.
The monthly payment on any fixed-rate loan comes from the standard amortization formula. The lender charges interest each month on the balance you still owe, and your payment covers that interest first, with the rest reducing the principal. Early on most of the payment is interest, and near the end most of it is principal. Because the calculation depends on the rate and the number of months, a small drop in APR can meaningfully cut both the payment and the total interest over the life of the loan.
The most useful number here is the lifetime interest savings, not just the monthly savings. A refinance that drops your payment by 40 dollars a month looks good, but if it does that by adding two years to the term, you might pay more interest in total. This tool separates the two effects so you can see them clearly: keep the term the same or shorter to capture the full benefit of a lower rate, or extend the term only when you genuinely need the lower monthly payment and accept the extra interest as the price of breathing room.
Refinancing makes the most sense when rates have fallen, when your credit score has improved since you took out the original loan, or when you were sold a high dealer rate you could now beat. It makes less sense late in a loan, when most of the interest is already paid, or when the old loan has a prepayment penalty or the car is worth less than you owe. Always weigh any refinance fees against the savings this calculator shows.
When to use it
- Checking if a lower rate offer from a bank or credit union actually beats your current auto loan.
- Seeing how much lifetime interest you would save by refinancing after your credit score improved.
- Comparing keeping the same term versus extending it, so you can see the true cost of a smaller payment.
- Deciding whether a dealer-arranged loan is worth refinancing away from a high markup rate.
- Estimating your new monthly payment before you apply, so there are no surprises.
- Weighing a shorter term that raises the payment but clears the loan and interest faster.
How to use the Car Loan Refinance Calculator
- Enter your current remaining balance, the loan payoff amount from your lender.
- Enter your current APR and the number of months left on the loan.
- Enter the new APR you have been offered and the new term in months.
- Read the monthly savings, both payments and the lifetime interest savings.
- Check the note about longer terms and the side by side table before you decide.
Formula & method
Worked examples
You owe $22,000 at 9.5% APR with 48 months left, and a credit union offers 5.5% APR for 48 months.
- Current monthly rate r = 9.5 / 100 / 12 = 0.0079167
- Current payment M = 22000 x 0.0079167 / (1 - (1.0079167)<sup>-48</sup>) = about 552.71
- Current total interest = 552.71 x 48 - 22000 = about 4,530.03
- New payment at 5.5% for 48 months = about 511.64, new total interest = 511.64 x 48 - 22000 = about 2,558.84
- Monthly savings = 552.71 - 511.64 = 41.07, interest savings = 4,530.03 - 2,558.84 = 1,971.19
Result: You save about $41.07 a month and about $1,971.19 in interest over the life of the loan.
You owe $18,000 at 8% APR with 36 months left, and you refinance to 6% APR but stretch the term to 60 months.
- Current payment at 8% for 36 months = about 564.05, current total interest = 564.05 x 36 - 18000 = about 2,305.96
- New payment at 6% for 60 months = about 347.99, a big drop in the monthly amount
- New total interest = 347.99 x 60 - 18000 = about 2,879.43
- Monthly change = 564.05 - 347.99 = 216.06 lower each month
- Interest change = 2,305.96 - 2,879.43 = -573.47, meaning about 573 dollars MORE interest
Result: The payment falls by about $216 a month, but the longer term costs about $573 more interest in total.
Monthly payment on a $20,000 balance by APR and term
| APR | 36 months | 48 months | 60 months | 72 months |
|---|---|---|---|---|
| 4% | $590.48 | $451.58 | $368.33 | $312.90 |
| 6% | $608.44 | $469.70 | $386.66 | $331.46 |
| 8% | $626.73 | $488.26 | $405.53 | $350.66 |
| 10% | $645.34 | $507.25 | $424.94 | $370.52 |
| 12% | $664.29 | $526.68 | $444.89 | $391.00 |
Interest saved on a $20,000 balance over 48 months by dropping the rate
| Rate drop | Old total interest | New total interest | Interest saved |
|---|---|---|---|
| 10% to 6% | $4,348.08 | $2,545.63 | $1,802.45 |
| 9% to 5% | $3,889.64 | $2,108.12 | $1,781.52 |
| 8% to 4% | $3,436.41 | $1,675.89 | $1,760.51 |
| 12% to 7% | $5,280.48 | $2,988.39 | $2,292.09 |
Common mistakes to avoid
- Judging a refinance by the monthly payment alone. A lower monthly payment can come from a longer term, not a better deal. Always check the total interest and the lifetime savings, not just how much lighter the monthly bill feels.
- Ignoring refinance and title fees. Some lenders charge application, title or state re-registration fees to refinance. Subtract those from the interest savings this tool shows to find your true net benefit.
- Refinancing very late in the loan. Most auto loan interest is charged in the early months. If you only have a year or two left, most of the interest is already behind you, so a refinance often saves very little.
- Forgetting the car may be worth less than you owe. If you are upside down on the loan, lenders may refuse to refinance or offer worse terms. Check your payoff balance against the car's current value before you apply.
Glossary
- Refinance
- Replacing your current auto loan with a new one, usually to get a lower rate or a different term.
- APR
- Annual percentage rate, the yearly cost of the loan expressed as a percentage of the balance.
- Term
- The number of months over which you repay the loan. A longer term means smaller payments but more interest.
- Amortization
- The process of paying off a loan with equal monthly payments split between interest and principal.
- Principal
- The amount you actually borrowed, separate from the interest charged on top of it.
- Payoff balance
- The exact amount needed to fully clear your current loan today, which the new loan pays off.
Frequently asked questions
How does the car loan refinance calculator work?
It uses the standard amortization formula to work out the monthly payment on both your current loan and the new one, using the same remaining balance. It then compares the two payments and the total interest of each to show your monthly savings and your lifetime interest savings.
Is refinancing my car loan actually worth it?
It is usually worth it when the new APR is meaningfully lower than your current one, your credit has improved, or you were sold a high dealer rate. Enter both loans here and look at the lifetime interest savings, then subtract any refinance fees to judge the real benefit.
Why does a lower monthly payment sometimes cost more interest?
A smaller monthly payment often comes from a longer term. Spreading the same balance over more months lowers each payment but means you borrow the money for longer, so the total interest can rise even at a lower rate. This tool shows both effects so you can see the trade-off.
What balance should I enter, the loan amount or what I owe now?
Enter your current remaining balance, also called the payoff amount, not the original loan amount. Your lender can give you the exact payoff figure. The refinance is calculated on what you still owe, not what you first borrowed.
Does this include refinance fees or taxes?
No. The calculator compares the loans on interest and payments only. If your new lender charges application, title or re-registration fees, subtract them from the interest savings shown to get your true net saving.
Should I keep the same term or extend it when I refinance?
Keep the same term or a shorter one to capture the full benefit of a lower rate and pay the least interest. Only extend the term if you genuinely need a lower monthly payment, and accept that the extra months usually add to the total interest.