Auto Refinance Calculator

How the calculator does the math

The calculator uses standard fixed-rate amortization — the same formula lenders use to turn a balance, a rate, and a term into a level monthly payment. It computes your current loan’s remaining payments, then computes a new loan on the same balance at the rate and term you enter, and puts the two side by side. Nothing is estimated or fudged; for the inputs you give it, the math is exact.

Here is the default example worked all the way through. Say you owe $22,000 at 11.5% APR with 54 months left. The formula prices that at $523.78 a month, or $28,284 across every remaining payment — $6,284 of it interest. Refinance the same $22,000 at 7.5% for the same 54 months and the payment drops to $481.28. That is $42.51 a month back in your budget and $2,295 less paid over the life of the loan. Both numbers improve because only the rate changed.

Now stretch the new loan to 72 months at that same 7.5%. The payment falls much further — $380.38, a $143.40 monthly saving — but you are paying interest for 18 extra months, so the lifetime saving shrinks from $2,295 to about $897. And if you extend to 72 months without a rate drop, staying at 11.5%, the payment still falls to $424.41, but the total cost rises to $30,557 — roughly $2,273 more than just keeping your current loan. Same balance, three very different outcomes. That spread is the whole reason this page shows lifetime cost next to the payment.

Where the inputs come from

Use your lender’s most recent statement or app for the APR and months remaining. For the balance, request a payoff quote from your current lender rather than reading the statement balance — the payoff figure includes interest accrued since your last payment and is the amount a new lender would actually pay off. Our step-by-step guide to refinancing a car loan covers where each number lives and what documents come next.

Reading the two numbers together

The calculator reports a monthly payment and a lifetime total, and they can point in different directions. The payment is what you feel every month; the total is what the loan actually costs. A lower rate at the same term improves both, and that is the clean win refinancing is built for. A longer term at any rate improves the payment while quietly working against the total.

When the two numbers disagree, neither is automatically right. If an $80 payment cut keeps you out of credit card debt, paying a few hundred dollars more over five years can be a rational trade — credit cards charge far more than any car loan. The calculator’s job is to make sure you see the price tag on that trade before you take it, because a payment-only comparison hides it completely. Lenders and dealers quote payments for exactly that reason.

What rate should you plug in?

The honest answer: you will not know your rate until a lender quotes you, and no calculator changes that. But you can plug in a realistic starting point instead of a guess. Experian’s State of the Automotive Finance Market report publishes average APRs by credit band each quarter; the table below is the Q1 2026 data (as of August 2026), which is the most recent release.

Two caveats. These are averages for purchase loans, not refinances, so treat them as a reference point rather than a forecast — the used-car column is usually the closer proxy for a refinance on a vehicle you already own. And an average is just the middle of a wide range: your quote depends on your score, the vehicle’s age and mileage, and how much you owe against what it is worth. A sensible approach is to run the calculator twice — once at your band’s average and once a point or two higher — and only count on the savings that survive the pessimistic run. Many lenders will then show an estimated rate with a soft credit inquiry, which does not affect your score, before you commit to a formal application.

One more piece of honesty: deep in the subprime range, refinancing often is not available at all — many lenders set minimum score requirements — and when it is, a 19–22% average APR leaves little room to beat an existing rate. If that is your situation, the better lever is usually a few months of on-time payments to climb a band before applying.

When refinancing pays — and when it doesn’t

The math tends to work in three situations. Your credit score has improved since you took the original loan — climbing even one band in the table above moves the average rate by several points. Market rates have fallen since you signed. Or your original loan was priced at a dealership markup you never shopped against. In each case you are replacing a rate with a genuinely lower one, which improves the payment and the lifetime cost at once.

It tends not to work when the loan is nearly paid off, because amortization front-loads interest — in the final year most of each payment is already principal, so there is little interest left for a better rate to save. It also fails when a payment drop comes entirely from a longer term, as the worked example above shows, or when fees eat the margin: the calculator deliberately excludes lender fees, title-transfer costs, and any add-ons, so ask every lender for the all-in figure and check your current contract for a prepayment penalty. And if you owe meaningfully more than the car is worth, many lenders will decline the loan regardless of what the payment math says. The full auto refinance guide works through each of these situations in more depth.

Five mistakes people make with refinance calculators

Comparing payments instead of totals. The most expensive mistake on this page. A payment can fall while the loan gets more expensive; you now know to read both numbers.

Using the statement balance instead of a payoff quote. The statement balance excludes interest accrued since your last payment. The gap is usually small, but the payoff quote is the real number, and it is one phone call.

Plugging in an advertised teaser rate. “Rates from” means the best rate offered to the strongest borrowers on the shortest terms. Use your credit band’s average and let a lender surprise you in the good direction instead.

Ignoring the term reset. Refinancing 54 remaining months into a fresh 72-month loan is a term extension, whatever the rate does. If you want a clean comparison, first run the new rate at a term matching your remaining months, then decide separately whether extending is worth it.

Stopping at the calculator. The result is a hypothesis, not a quote. Rates differ meaningfully between lenders for the same borrower, which is why comparison shopping matters — see our rundown of the best auto refinance companies for how the major players differ on rates, fees, and credit requirements.