Auto Refinance Interest Savings Calculator
See how much interest a lower rate saves when you refinance your existing car loan over the same remaining term.
A worked example
Running this tool on current national benchmarks (Federal Reserve / Freddie Mac via FRED (St. Louis Fed)) — swap in your own numbers to see how the result moves.
- Current loan balance
- $22,000
- Current interest rate
- 9.50%
- New interest rate
- 6.50%
- Months remaining
- 48
$30.98 lower payment for 48 months
- Current payment$552.71
- New payment$521.73
- Monthly saving$30.98
How the total interest saved changes with current loan balance
Holding the other inputs at the example above, here is how the result moves as current loan balance changes.
| Current loan balance | Total interest saved | Current payment |
|---|---|---|
| $10,000 | $676 | $251.23 |
| $15,000 | $1,014 | $376.85 |
| $20,000 | $1,352 | $502.46 |
| $35,000 | $2,366 | $879.31 |
| $45,000 | $3,042 | $1,130.54 |
The math behind it
Using your current balance and the months remaining, the calculator computes the fixed monthly payment at your existing rate and again at the new rate, keeping the same payoff term. The difference in payments, multiplied by the months left, is your total interest savings. It also tracks the balance and cumulative interest year by year for each rate so you can see where the gap opens up.
Assumptions & limits
- The new loan keeps the same remaining term you enter — refinancing to a longer term can lower the payment while raising total interest.
- Refinance costs such as title transfer, lender, or state re-registration fees are excluded; subtract them from the shown savings.
- Both rates are fixed for the remaining term.
- The comparison assumes you refinance the current balance exactly, with no cash-out or added fees rolled in.
- Any gap between your old loan's payoff quote and its statement balance is not modeled.
Common questions
Does refinancing my car reset the loan and cost me more?
It can, if you extend the term. This calculator holds the remaining months constant, so it isolates the savings from a lower rate alone. If you stretch the payoff to shrink the monthly payment, you may pay more total interest even at a lower rate — enter a longer remaining term to see that effect.
Why doesn't the savings include fees?
Auto refinances often carry a title transfer or re-registration fee, and some lenders add a small origination cost. The estimate shows gross interest savings so you can compare it against whatever fees your lender quotes. If fees exceed the savings, refinancing is not worth it.
Is there a point where my car is too old to refinance?
Many lenders cap refinancing by vehicle age or mileage, and a loan that is far into its term has little interest left to save. Refinancing pays off best early in the loan and when your credit or rates have improved meaningfully since you bought.