π° Cash Back vs Low Interest Calculator
Rebate plus a higher rate, or no rebate plus a promo rate: which costs less?
Winner
Estimates for planning only, not financial advice.
How to Use This Calculator
Dealers often offer you a choice: take a cash rebate and finance at the regular rate, or skip the rebate and get a promotional low rate. This calculator prices both options with the same amortization math your lender uses, then shows the monthly payment, total interest, and total cost of each so the winner is obvious. Enter the vehicle price, your down payment, the rebate amount, the two APRs, and the loan term.
Enter the Vehicle Price and your Down Payment. These apply to both options, so the comparison stays apples to apples.
Enter the Cash Rebate and the APR with Rebate. This is Option A: you finance price minus rebate minus down payment at the higher rate.
Enter the Promo APR for Option B, where you give up the rebate and finance the full price minus down payment at the low rate.
Pick your Loan Term and read the verdict. The winner is the option with the lower total cost, and the breakdown shows exactly where the difference comes from.
The Math Behind the Comparison
Both options use the standard loan amortization formula, where P is the amount financed, r is the monthly rate, and n is the number of months. The rebate option starts with a smaller P but a bigger r; the promo option starts with a bigger P but a smaller r. Total interest is the tiebreaker: whichever option pays less interest wins, because the down payment is identical on both sides. The monthly payment comparison can mislead you, since the option with the lower monthly payment is not always the one with the lower total cost.
Worked Example
Take a $25,000 car with no down payment, a 60-month term, a $2,000 rebate at 5.9 percent APR, or a 0.9 percent promo rate with no rebate. Option A finances $23,000 at 5.9 percent: the monthly payment is $443.59 and the total paid is $26,615. Option B finances $25,000 at 0.9 percent: the monthly payment is $426.27 and the total paid is $25,576. The promo rate wins by about $1,039 in total cost, and it also has the lower monthly payment. Now change the term to 84 months: the rebate option's smaller balance matters more over time, and the gap narrows or can flip depending on the rates. That is why you should always rerun the comparison for the term you will actually sign.
Negotiating Tips
Settle the vehicle price before discussing incentives. Dealers sometimes inflate the price to "fund" the rebate, which erases its value. Ask for the buy rate on the promotional financing and get pre-approved by your bank or credit union first, so you know whether the dealer's standard rate with the rebate is actually competitive. If you plan to pay the loan off early, lean toward the rebate: you keep the full benefit of the smaller balance, while a low rate saves you less when the loan is short-lived. And if the dealer offers a third path, a dealer discount stacked with the promo rate, price that too, because it can beat both factory options.
Estimates for planning only, not financial advice.
Frequently Asked Questions
Should I take the cash rebate or the low interest rate?
It depends on the numbers, not on which offer sounds better. A large rebate with a higher rate usually wins on longer terms and higher rates, because the rebate cuts the amount you finance from day one. A 0 percent or near-zero rate usually wins when the rebate is small or the loan term is short. Run both options with your actual rate and term instead of guessing.
How does a cash rebate change my loan?
A cash rebate is applied directly against the purchase price, so you finance less money. On a $25,000 car with a $2,000 rebate, you borrow $23,000 instead of $25,000. You still pay interest at the higher rate, but interest is charged on a smaller balance for the whole term, which is where the savings come from.
Can I get both the rebate and the low rate?
Usually not. Manufacturers design these as either-or incentives: the rebate comes with standard financing rates, and the promotional rate requires giving up the rebate. Occasionally a dealer discount can be stacked with the promotional rate, so it is always worth asking, but the factory rebate and the factory rate are almost never combined.
Does the loan term change which deal wins?
Yes, and this is the key insight the calculator reveals. The longer the term, the more total interest you pay, which favors the rebate because it shrinks the financed amount. On short terms like 36 months, total interest is small either way, so a 0 percent rate often wins. Always compare using the term you actually plan to take.
What about my down payment in this comparison?
A down payment reduces the financed amount under both options equally, so it does not change which option wins, but it does lower both monthly payments. Enter your planned down payment and the calculator applies it to both sides, giving you the real monthly numbers you would see at the dealership.
Are there taxes or fees that change the answer?
Sales tax is charged on the price after the rebate in most states, which slightly favors the rebate option. Dealer fees apply equally to both options and cancel out of the comparison. Because the tax treatment is nearly identical on both sides, it rarely flips the winner, but your state may differ.