How to use this calculator
- From your latest statement, enter the principal balance after your last payment, the interest rate and the number of payments left. The calculator shows the payment those work out to, so you can check them against your statement.
- From the lender’s offer, enter the new interest rate (not the APR), the term in months, and the fees: the lender’s, your state’s fee to move the title and lien, and any fee your current lender charges to pay the loan off early. Choose whether you’ll add the fees to the loan or pay them up front.
- To see what paying faster does, tick Pay extra and enter an amount each month, a one-time payment now, or both. The calculator ranks paying extra on your loan, refinancing, and doing both.
- Under More options, enter the payment you actually make if it differs from the worked-out one, or the number of months until you may sell or trade in the car.
The numbers already filled in are an example. Replace them with your own.
How it's calculated
Both loans are run month by month, as an amortization schedule. Each payment pays that month’s interest first, a twelfth of the yearly rate times the balance, and the rest reduces the balance; the last payment is whatever is left, so the balance ends at exactly $0. Your loan’s payment is the one that repays what you owe over the payments left; the new loan’s repays its amount over its term. Fees added to the loan are part of its amount.
For each choice, the cost from now is the interest it charges plus, for a refinance, its fees. That comes to the same as what you pay plus what you would still owe, less what you owe now, so a new loan that lowers the payment by stretching the debt gets no credit for the part of the drop that is only a slower payoff. With a sale month, the costs stop there.
An example
You owe $26,000 at 8.4% with 36 months left, a payment of $819.55. Kept as it is, it costs $3,504 in interest from now. A 36 months refinance at 7.47% with $100 of fees added to the loan borrows $26,100 at a payment of $811.51, and costs $3,214 in interest and fees: $289 less. It pulls ahead after 6 months. Above 8.13%, the same refinance would no longer save money.
A longer term
Stretched to 48 months, the same rate lowers the payment to $630.70 but costs $4,274, $770 more than keeping your loan. It is ahead after 7 months and behind again after 19 months. The term table under the results shows the payment and the cost at each length.
Paying extra
An extra payment goes to principal after the month’s interest, so it shortens the loan rather than lowering the payment, and every extra dollar saves interest at that loan’s rate. Paying $100 extra a month on your loan pays it off 4 months sooner and costs $3,075; doing it on the refinanced loan costs $2,836. A one-time payment is made now, and with a refinance it lowers what you borrow.
Assumptions and limits
- Interest is charged monthly, a twelfth of the interest rate on the balance, and the next payment on your loan and the first on a new one both fall a month from now. Many car loans charge interest by the day, so each day the new loan’s first payment comes later than a month adds about its interest a day, shown with the results ($5.34 in the example).
- Both rates are interest rates, not APRs: an APR already counts a lender’s fee, which goes in Fees here.
- The loan is a simple-interest loan. On a precomputed loan, extra payments may not lower the interest until you pay it off in full, and paying it off early can save less than this shows.
- Rates stay the same for the whole loan; a variable rate isn’t modeled.
- An extra payment is assumed to go wholly to principal and to shorten the loan. If your statement shows an extra moving your next due date instead, ask the lender in writing to apply it to principal. No prepayment penalty is counted for paying extra.
- Fees are one amount. Add-ons such as GAP coverage or a service contract are not fees, and the calculator doesn’t price them.
- Costs are added up as dollars. Money a lower payment frees, or the extra you pay, earns nothing here.
- With a sale month, the comparison stops then and counts what you’d still owe on each loan. What the car is worth, and whether you owe more than that (negative equity), isn’t estimated.
- It doesn’t price cash out, a second offer, a deferred first payment, or an APR worked out from fees, and it doesn’t check whether a lender would approve the loan.
- Everything is before tax. The car loan interest deduction is described in the questions below, not computed.
- The default current rate is the Federal Reserve’s average for 60-month new car loans at commercial banks in August 2024, its highest reading since the series began in 2006; the default new rate is the same release’s 48-month average for August 2026. Both are new-car rates, and a lender may price a refinance of a used car higher. The default fee is an example, not an average.
Input field details
What to enter in each box, where to find the number, and how this calculator treats it. When two calculators give different answers from the same numbers, it's usually because they handle one of these differently.
What you owe now
The principal balance on your car loan after your last payment.
Where to find itYour latest loan statement, often labelled "principal balance".
How this tool treats itThe comparison starts here, with your next payment a month away. A payoff quote is a different, higher number: it adds the interest from your last payment to the day the quote names, which is what a new lender sends your current one. Each day adds about the interest a day shown with the results.
Allowed range$500 to $500,000
Interest rate
The interest rate on your current loan, to two decimals (8.4 or 6.49).
Where to find itYour statement or your contract. If your contract shows only an APR and you paid no loan fee, the APR is the same number.
How this tool treats itThe APR is the interest rate plus the lender’s fees, spread over the loan as a yearly rate. Each month’s interest here is a twelfth of the interest rate on the balance, rounded to the cent and paid before principal.
Allowed range0% to 30%
Not includedA rate that changes: the loan is modeled at the rate you enter for its whole life.
Months left
How many monthly payments are still due on your current loan.
Where to find itYour statement, or count the months from your next payment to the loan’s last payment date.
How this tool treats itYour payment is worked out from what you owe, the rate and the payments left, and shown under the loan so you can check it against your statement.
Allowed range1 to 96 payments
New rate
The interest rate in the new lender’s offer, not the APR.
Where to find itThe offer or the loan disclosure. If you only have the APR, enter it here and leave that lender’s fee out of Fees, so the fee is not counted twice.
How this tool treats itRefinancing replaces your loan with a new one: the new lender pays off what you owe, and you repay the new loan at its own rate and term. The new loan’s first payment is taken to fall a month from now, as your next payment would.
Allowed range0% to 30%
New term
How many monthly payments the new loan has.
Where to find itThe offer.
How this tool treats itA longer term lowers the payment and raises the interest you pay over the loan, because the balance comes down more slowly. The term table shows the payment and the cost for 24 to 84 months at the new rate.
Allowed range12 to 96 months
Fees
Every fee the refinance costs you: the new lender’s, the state’s fee to move the title and lien, and any fee your current lender charges to pay the loan off early.
Where to find itThe new lender’s offer, your state’s motor vehicle agency, and the prepayment line in your current contract’s federal disclosure, which says whether you could pay a penalty for paying early.
How this tool treats itNot add-ons such as GAP or a service contract. The break-even is the first month refinancing has cost you less than keeping your loan, counting these fees and the difference in what you would still owe on each.
Allowed range$0 to $10,000
Pay the fees
Whether the fees are added to the new loan or paid up front, as the offer allows.
How this tool treats itAdded to the loan, you pay interest on them for the life of the new loan; paid up front, they cost the same fees without that interest. Either way they count in full as a cost of refinancing.
Pay extra
Tick it to compare paying extra on your loan, on the new loan, or both.
How this tool treats itEvery option is ranked by its cost from now: the interest you would pay from now on, plus any fees. With a sale month, it is the cost to that month, and the comparison counts what you would still owe on each loan then.
Extra each month
The amount you would add to every monthly payment.
How this tool treats itAn extra payment is anything you pay above the payment due. It is assumed to go wholly to principal after the month’s interest, so the loan ends sooner and your payment stays the same. That assumes a simple-interest loan, where interest is charged on the balance you still owe, so paying it down early lowers the interest. If your statement shows an extra moving your next due date instead, ask the lender in writing to apply it to principal.
Allowed range$0 to $10,000 a month
Lump sum
A lump sum you would pay toward the loan now.
How this tool treats itWith a refinance, it is paid before the new loan, so it lowers what you borrow. A payment of at least what you owe pays the loan off now. On a precomputed loan, the interest for the whole term is worked out when the loan is made and added to what you owe, so paying early saves only the part of that interest the lender refunds. Federal law (15 U.S.C. 1615) requires a refund when you pay in full, figured at least as favorably as the actuarial method only on precomputed loans longer than 61 months; for shorter ones your state’s law or the contract sets it. Extra payments on a precomputed loan may not lower the interest until you pay the loan off in full.
Allowed range$0 to $500,000
My payment is different
Tick it if the payment on your statement differs from the one worked out under your loan.
How this tool treats itWhen ticked, the payment field starts at the worked-out payment, so nothing changes until you type your own.
Your monthly payment
Your loan’s monthly payment, to the cent, without add-ons billed with it.
Where to find itYour statement.
How this tool treats itA larger payment pays your loan off sooner. A payment more than $1.00 below the one the balance, rate and payments left work out to would not repay the loan in time, so the worked-out payment is used instead and a note says so.
Allowed range$0 to $20,000 a month
I may sell or trade in the car first
Tick it if you expect to sell or trade in the car before either loan is paid off.
How this tool treats itThe comparison then stops at that month and counts what you would still owe on each loan. What the car sells for is the same either way, so it is not asked.
Months until then
How many months from now you expect to sell or trade in the car.
How this tool treats itA sale after both loans are paid off gives the same answer as no sale.
Allowed range1 to 96 months
Questions
Is it worth refinancing my car loan?
Does refinancing to a longer term save money?
Is it better to refinance my car or pay extra?
Why does the break-even differ from the fees divided by the payment saving?
Should I enter the APR or the interest rate?
Is there a penalty for paying off a car loan early?
What happens to the car loan interest deduction if I refinance?
What is a payoff amount?
Version history
- October 29, 2026 (version 1.0.0): First version. Compares keeping a car loan with refinancing it, counting fees and what you’d still owe at a sale, with break-even, the highest rate that saves, terms, and extra monthly or one-time payments ranked.