Car loan refinance calculator: compare your current auto loan against a new rate and term to see monthly savings and total interest. Free, private, no signup.
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Every figure above is calculated locally in your browser from the assumptions shown. No inputs are sent anywhere. See the methodology section below for the formulas used.
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Refinancing a $20,000 auto balance from 7.5% to 5% over 48 months cuts the payment from $483.58 to $460.59, saving $22.99 per month and $1,103.62 in total interest. The savings grow with the balance and the rate drop. Run your own numbers in the BoringToolsKit refinance savings calculator.
Refinance savings come from the rate drop only when the term stays the same; stretching the term can raise total interest. (Source: CFPB)
A 2.5 point rate drop on $20,000 over 4 years is worth about $1,100. (Source: BoringToolsKit calculation methodology)
Lenders may charge refinance fees that offset part of the savings. (Source: BoringToolsKit calculation methodology)
$20,000 refinanced from 7.5% to 5%: $22.99 saved per month.Refinancing $20,000 saves $27.84 per month.
Transparent methodology
How this calculator works
Formula
Monthly payment = balance x r/1200 / (1 - (1 + r/1200)^-months), computed at the old and new rate; savings = old payment - new payment.
Worked example
Refinance $20,000 from 7.5% to 5% over 48 months: payment drops from $483.58 to $460.59, saving $22.99 a month and about $1,104 over the loan.
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A worked example: $20,000 refinanced
Say you owe $20,000 with 48 payments left. At 8.50% your payment is $20,000 x 0.0070833 / (1 - 1.0070833^-48), which works out to $492.97 per month and $3,662 in total interest. At 5.50% the same 48 months cost $465.13 per month and $2,326 in interest.
The headline saving is $27.84 per month, or $1,336 over the life of the loan - which is exactly the gap between the two interest totals. Check it: $3662 - $2326 = $1336. If the refinance charges a $500 origination fee, the net benefit drops to $836, and you can immediately see whether that is worth the paperwork.
Term matters as much as rate. Stretch the same $20,000 to 60 months at 5.50% and the payment falls to $382.02, a $28.31 drop versus staying at 8.50% for 60 months ($410.33). But total interest over 60 months is $2,921, more than the 48-month loan. The calculator keeps the term fixed precisely so the comparison isolates the rate effect.
What the monthly saving does not show
Refinancing resets your amortization schedule. If you are 30 months into the original loan, you have already paid mostly interest and built real equity; restarting at month 1 of 48 means the early payments skew back toward interest. On the $20,000 example above, the new loan's first payment at 5.50% allocates only about $91 of the $465.13 to principal - less principal reduction than your old loan was delivering by month 30.
Fees arrive in forms this calculator ignores: origination fees (often 1-2%, so $200-$400 on a $20,000 loan), title re-filing ($15-$50 in most states), and prepayment penalties on some older contracts. A $28 monthly saving needs roughly a year just to cover a $350 fee package.
Lenders also price by credit tier, not the advertised rate. A borrower at 780 FICO may see 5.50% while 660-689 lands near 9-11%, in which case refinancing from 8.50% could increase the payment. Get an actual offer before acting; the inputs here assume both quotes are real and final.
