Cash Back or Low Interest Calculator

How This Calculator Compares the Two Offers

Short answer: the calculator prices out the exact same vehicle two ways — once with the rebate applied and financed at your standard rate, once with no rebate but financed at the promotional rate — then compares the total dollars you'd pay across the whole loan, not just the monthly payment.

For each scenario, the amount financed is:

That loan amount is then run through the standard amortizing-loan payment formula:

Total cost for each offer is the vehicle price minus any rebate, plus tax, plus fees, plus total interest paid over the life of the loan — an apples-to-apples number for both scenarios since the price and fees are identical either way. Whichever total is lower is the better deal in dollar terms.

The Break-Even Cash Back tab runs the algebra in reverse: holding the price, term, and both APRs fixed, it solves directly for the rebate amount that would make the two totals equal, using the fact that a fixed-rate loan payment is linear in the loan amount — no trial and error, no approximation.

A Full Worked Example

Say you're buying a $30,000 vehicle with $2,000 down, no trade-in, in Texas (6.25% sales tax, $300 in title and doc fees rolled into the loan), over a 60-month term.

• Cash-back offer: $1,500 rebate, financed at the standard 6.5% APR → sales tax $1,781.25 (Texas taxes the price after the rebate: $28,500 × 6.25%) → monthly payment $559.22, total interest $4,972.25, total cost $35,553.50.
• Low-interest offer: no rebate, financed at a 1.9% promotional APR → sales tax $1,875.00 (full $30,000 price, since there's no rebate here to exempt) → monthly payment $527.58, total interest $1,479.87, total cost $33,654.87.

The low-interest offer wins here by $1,898.63 over the life of the loan — the 4.6-point rate gap on a five-year loan outweighs the $1,500 upfront rebate, even after Texas's rebate-tax exemption shrinks the cash-back offer's tax bill a little. Run the Break-Even tab on these same numbers and it tells you the rebate would need to be about $3,022 before cash back caught up. Note the two offers show slightly different sales-tax amounts above ($1,781.25 vs. $1,875.00) even on the identical vehicle — that's the hidden rule in the next section, not a mistake.

The Hidden Rule Most Buyers Miss: Sales Tax on the Rebate

Short answer: it depends entirely on your state. Roughly 20 states charge sales tax only on the price after the rebate is subtracted, while the rest — including some of the biggest car markets, like California and New York — charge tax on the full price before the rebate.

This surprises a lot of buyers because a trade-in works differently and more consistently: most states let a trade-in's value reduce your taxable amount, so it's natural to assume a cash rebate works the same way. It doesn't always, because in states that tax the rebate, the manufacturer's payment is treated as a form of payment toward the price — similar to using a coupon — rather than an actual reduction in the car's selling price for tax purposes.

Based on figures compiled by Edmunds (via CarsDirect), here's the state-by-state breakdown this calculator uses:

• Rebate reduces the taxable amount (tax charged after the rebate): Alaska, Arizona, Delaware, Iowa, Kansas, Kentucky, Louisiana, Massachusetts, Minnesota, Missouri, Montana, Nebraska, New Hampshire, Oklahoma, Oregon, Pennsylvania, Rhode Island, Texas, Utah, Vermont, Wyoming.
• Rebate does not reduce the taxable amount (tax charged on the full price): every other state, including California, New York, and Florida.
• Trade-in does not reduce the taxable amount (a separate, shorter list): California, District of Columbia, Hawaii, Kentucky, Maryland, Michigan, Montana, Virginia.
• No state sales tax on vehicles at all: Alaska, Delaware, Montana, New Hampshire, Oregon.

Notice Kentucky and Montana appear on more than one list, and a handful of states (Alaska, Delaware, Montana, New Hampshire, Oregon) have no sales tax at all, which makes the rebate question moot there. This calculator applies all of these rules automatically based on the state you select — pick your state and the sales-tax math (and the note under your results) updates to match.

Cash Back vs. Low Interest: Which Should You Choose?

Short answer: cash back tends to win on shorter loans and smaller rate gaps; low interest tends to win on longer loans and wider rate gaps. Run your own numbers above rather than trusting a rule of thumb — but here's the general shape of it:

Cash back usually comes out ahead when:

• You plan to pay off the loan quickly, or finance for 36 months or less.
• The gap between the standard rate and the promotional rate is small (roughly under 3–4 percentage points).
• You have a large trade-in or down payment, so the loan amount — and therefore the interest either rate would generate — is small to begin with.
• You don't qualify for the promotional rate, which usually requires strong credit.

Low interest usually comes out ahead when:

• You're financing over 60 months or longer, giving the rate gap more time to compound.
• The rate gap is wide — a 0%–2% promotional rate against a 6%+ standard rate is the classic case.
• The loan amount is large relative to the rebate on offer.

Either way, the deciding factor is always the same: the rebate is a one-time number, while the rate difference is a recurring cost multiplied by every month you carry the loan. The longer and larger the loan, the more that recurring difference tends to dominate.

Is 0% APR Financing a Special Case?

Short answer: not mathematically — it's simply the low-interest offer taken to its logical extreme, and this calculator handles it exactly the same way. Enter 0 in the Promotional APR field and every formula above still applies.

What is different about 0% offers is eligibility and availability. Manufacturers typically reserve 0% financing for buyers with excellent credit (often 720+ FICO), cap it at shorter terms (36–48 months is common, even when longer terms are available at higher rates), and may restrict it to specific trim levels or model years the manufacturer is trying to move. A small positive promotional rate — 1.9% to 3.9% is common — usually has more flexible qualifying criteria and longer available terms, which is worth checking against 0% offers that only apply to a shorter term than you actually want.

Common Mistakes When Comparing These Offers

• Comparing only the monthly payment. A lower monthly payment on a longer term can still cost more in total — always compare total cost, not just the payment, especially if the two offers use different terms.
• Assuming the rebate reduces your taxable price. As covered above, it almost never does — leaving this out understates the true cost of the cash-back option.
• Not checking whether both offers apply to the same term. Some promotional rates are only available on shorter terms than the standard financing — comparing a 36-month low-rate offer against a 72-month standard-rate scenario isn't a fair comparison.
• Forgetting the rebate can sometimes stack with dealer negotiation. Whether it does depends on the manufacturer and dealer — always ask directly and get it in writing rather than assuming either way.
• Ignoring your own credit eligibility. The promotional rate in the ad is usually the best available rate for the most qualified buyers — confirm your actual approved rate before running the comparison, since a lower advertised rate you don't qualify for isn't a real option.

Frequently Asked Questions

This calculator is provided for educational and estimation purposes only and does not constitute financial advice. Rebates, promotional rates, and tax rules vary by manufacturer, lender, and state — confirm exact terms with your dealer or lender before making a decision.