Auto Refinance Calculator
Compare your current auto loan against a refinance offer: monthly payment change, lifetime cost difference, and break-even on fees.
How to Use
- Enter your current auto loan's remaining balance, its interest rate, and how many months remain on it.
- Enter the new interest rate and term you're considering, and any refinance fees (application, title, or lender fees) you'd pay out of pocket.
- The result shows both monthly payments, the monthly change, the lifetime cost difference between keeping your current loan and refinancing, and how many months it takes for the monthly savings to recover the fees — or a clear note if your new payment doesn't decrease.
Formula
- Current payment
- current_payment = current_balance × current_monthly_rate ÷ (1 − (1 + current_monthly_rate)^−current_months_remaining)
- New payment
- new_payment = current_balance × new_monthly_rate ÷ (1 − (1 + new_monthly_rate)^−new_months)
- Lifetime cost difference
- (new_payment × new_months + refinance_fees) − (current_payment × current_months_remaining)
- Break-even months
- refinance_fees ÷ (current_payment − new_payment) [only when the new payment is lower]
Worked Example
An $18,000 balance at 9% with 36 months remaining, refinanced into a new 48-month loan at 6% with $200 in fees.
- Current payment (36 months remaining at 9%): ≈ $572.40/month
- New payment (48-month term at 6%): ≈ $422.73/month
- Monthly change: $422.73 − $572.40 ≈ −$149.66 (a decrease)
- Break-even: $200 ÷ $149.66 ≈ 1.3 months
- Lifetime cost difference: (new loan's total cost + fees) − (cost of finishing out the current loan) ≈ −$115.16
Result: Monthly payment change: −$149.66 (decrease) / Lifetime cost difference: −$115.16 / Break-even on refinance fees: 1.3 months
About This Tool
What this tool does
This calculator compares the cost of keeping your current auto loan as-is against refinancing into a new rate and term, showing the monthly payment change, the total lifetime cost difference between the two paths, and how many months it takes the monthly savings to pay back any refinance fees.
When to use it
Use it whenever you're offered a refinance on your car loan, especially if your credit has improved since you originally financed — but always check the lifetime cost, not just the monthly payment, since extending the term can lower the payment while still costing more overall.
What the result means
A negative monthly payment change means your payment goes down; a negative lifetime cost difference means refinancing costs less overall than keeping your current loan (both are "good" directions here). Break-even is how long it takes your monthly savings alone to recover what you paid in refinance fees.
Assumptions & limitations
Refinance fees are modeled as paid out of pocket, not rolled into the new loan balance — if you plan to finance fees into the new loan, add that amount to the balance you refinance instead of entering it separately here. This tool doesn't account for any change in your vehicle's value, gap insurance, or extended warranty implications from refinancing, and it is not a loan offer, rate quote, or refinance recommendation.