Cash Back or Low Interest Calculator
Dealers love offering a choice: a cash rebate or promotional low-APR financing — never both. This calculator runs your deal down both roads, including tax, fees, and trade-in, and tells you which one leaves more money in your pocket over the life of the loan.
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Get ratesHow the comparison works
Both routes buy the same car; they differ only in financing. The cash-back route subtracts the rebate from what you finance but pays the standard interest rate. The low-APR route finances the full amount at the promotional rate. Because a rebate saves money on day one while a low rate saves it slowly over the term, the winner depends on rebate size, the rate gap, and how long the loan runs — so the honest comparison is total cost: everything you pay up front plus every monthly payment.
How it’s calculated
Sales tax = tax% × (price − trade-in), the treatment used in most states (manufacturer rebates usually do not reduce the taxable price). Financed amount = price − down − trade-in [− rebate, cash-back route] + tax and fees if rolled in. Payment = L × r ÷ (1 − (1 + r)−n) at each route’s monthly rate. Total cost = up-front cash + payment × n. The verdict is the difference between the two totals.
Estimates only — some states tax the pre-trade-in price or treat rebates differently, and promo rates require top-tier credit. Confirm the contract numbers.
Worked example
A $38,000 car with $4,000 down, 6% sales tax ($2,280), $500 fees rolled in, over 60 months. Cash-back route: a $2,500 rebate cuts the loan to $34,280 at 7.5% — $686.90 a month, $6,934 interest, $45,214 total. Low-APR route: finance $36,780 at 2.9% — $659.26 a month, $2,775 interest, $43,555 total. Here the low rate wins by $1,658.74, because a 4.6-point rate gap over five years outweighs the $2,500 rebate. Shorten the term or shrink the rate gap and the rebate takes the lead.
Common mistakes
- Comparing monthly payments instead of total cost — the low-APR payment is often lower even when it costs more overall.
- Assuming the rebate reduces sales tax; in most states it does not.
- Ignoring the third option: take the rebate and finance through a bank or credit union at a competitive rate.
- Forgetting that promo APRs are credit-tiered — if you do not qualify, the whole comparison changes.
Where it is used
- Choosing between manufacturer incentives on a new car or truck.
- Checking whether outside financing plus the rebate beats both dealer offers.
- Negotiating: knowing the dollar gap between offers is leverage at the desk.
Frequently asked questions
When does cash back beat the low APR?
When the rebate is large relative to the loan, the term is short, or the standard rate isn’t much higher than the promo rate. Small rebate + long term + big rate gap favors the low APR. There is no universal answer — the totals depend on your exact numbers, which is what this calculator compares.
Can I take both the rebate and the promotional rate?
Usually not — manufacturers typically make you choose between customer cash and subsidized financing. Occasionally stacked offers exist on slow-selling models. If you can genuinely take both, this comparison is moot: take both.
What if I can get a cheaper loan from my bank or credit union?
Then compare cash back + your outside rate against the dealer’s low APR. Enter your credit-union rate as the standard APR — taking the rebate and financing elsewhere at a decent rate is often the winning combination.
Does paying the loan off early change the answer?
Yes. Early payoff shrinks the interest advantage of the low-APR route, making the up-front rebate relatively more valuable. If you plan to pay the car off in a year or two, lean cash back; the rebate is yours regardless of how long the loan lasts.
Is the rebate taxable or taxed in the price?
In most states a manufacturer rebate does not reduce the taxable sale price — you pay sales tax on the pre-rebate price, which is how this calculator models it. A dealer discount, by contrast, usually does lower the taxable price. A few states differ, so check your DMV’s rules.