Car Refinance Calculator

Car refinancing is different from shopping for a new vehicle. You already have a loan, a remaining term, and a payoff balance. A refinance replaces that remaining debt with a new auto loan, possibly at a lower rate, a different term, with financed fees, or with cash in or cash out. This calculator compares the two paths: keep paying the current loan, or replace it with the proposed refinance.

The primary result is the estimated monthly savings or monthly increase. The supporting lines are just as important: current monthly payment, new monthly payment, current and new total interest, interest savings after fees, total payment savings, and a fee break-even period when fees exist and the monthly payment falls. For a brand-new purchase, use the auto loan calculator or car loan EMI calculator. If the refinance is part of a larger debt plan, compare it with the debt payoff calculator.

How to use this calculator

Enter the balance left on loan from your payoff quote or current principal balance. Then enter the remaining term and rate on your current loan. Add the new term and new rate from the refinance quote. Use cash out (or cash in) for principal adjustments: positive means you borrow extra cash, while negative means you bring cash to reduce the new balance. Add refinance fees that will be financed into the new loan.

The calculator validates that the existing balance is positive, both terms are positive, both rates are nonnegative, and fees are nonnegative. It also checks that the new loan amount is positive after cash in or cash out. The new loan amount is the current balance plus cash out or cash in plus financed fees. This matches how the calculator builds the replacement loan before amortizing it.

Formula

For each loan, the monthly rate is the annual rate divided by 12, and the payment for a positive rate is:

$\text{payment} = \text{principal} \times \frac{\text{monthly rate} \times (1 + \text{monthly rate})^{\text{months}}}{(1 + \text{monthly rate})^{\text{months}} - 1}$

The new principal is:

$\text{new loan amount} = \text{balance} + \text{cash in or out} + \text{refinance fees}$

Monthly savings is:

$\text{monthly savings} = \text{current monthly payment} - \text{new monthly payment}$

Interest savings after fees is:

$\text{interest savings after fees} = \text{current interest} - \text{new interest} - \text{refinance fees}$

Total payment savings is:

$\text{total payment savings} = \text{current total payments} - \text{new total payments} - \text{cash in or out} - \text{refinance fees}$

If monthly savings is positive and fees are positive, break-even months equals fees divided by monthly savings.

Worked example

Use the default inputs: $32,000 balance, 72 months remaining at 8.5 percent, refinanced into 60 months at 4.5 percent, with $0 cash in or out and $0 financed fees. The current payment is $568.91 per month. The proposed new payment is $596.58 per month. Monthly savings is therefore -$27.67, so the calculator presents the primary result as an estimated monthly increase of $27.67.

The total interest story is different. Staying with the current loan would cost about $8,961.40 of remaining interest. The new loan costs about $3,794.60 of interest. With no refinance fees, interest savings after fees is $5,166.80. This is a classic refinance tradeoff: a shorter, lower-rate loan can raise the monthly payment but reduce total interest substantially.

Refinancing context

Refinancing can help when market rates have fallen, your credit profile has improved, the original dealer financing was expensive, or you need to change the loan term. It can hurt when the new term is too long, fees are high, or the car is worth less than the lender will accept. The calculator does not check loan-to-value, mileage, title status, or credit criteria; it only compares the cash-flow math.

Be careful with cash-out refinancing. Adding cash out increases the new loan amount and can make the vehicle carry debt for longer. Cash in does the opposite, but it uses savings today. If your goal is simply a lower payment, test whether the total interest and total payment savings remain positive after the term change. Then place the proposed payment in the budget calculator so it is judged against insurance, fuel, repairs, and other obligations.

Tips for refinance decisions

• Use a payoff quote when possible; the balance on a statement can differ from the amount needed to close the old loan.
• Compare offers using APR, term, fees, and whether fees are paid upfront or financed.
• Watch for a lower payment created mainly by extending the term.
• Consider how long you plan to keep the vehicle; break-even matters less if you sell soon.
• Confirm there is no prepayment penalty or title-processing issue on the current loan.

Sources

• CFPB Regulation Z, 12 CFR Part 1026 — current through 2026-07-09; APR, finance-charge, payment, disclosure and credit terminology; user-supplied illustrative loan formulas are not lender quotes.
• Calculation scope: The equations and assumptions described above are applied only to values entered in the form. No live rates, prices, tax rules, lender terms, or accounting classifications are fetched. Results are user scenarios, not quotes or prescribed classifications.