Cash Back or Low Interest Calculator

How it works

Comparing a rebate with a lower interest rate

A cash rebate reduces the purchase cost or amount financed, while a promotional interest rate changes the cost of borrowing over time. Compare both offers using the same vehicle, down payment, and repayment term. The more attractive monthly payment is not necessarily the lower total-cost offer. Include the applicable fees and tax treatment before drawing a conclusion from the difference.

Compare offers: formula and assumptions

Compare down payment plus all scheduled payments under each offer.

This comparison excludes taxes, fees, early payoff, and differences in eligibility.

Payment budget & vehicle price: formula and assumptions

Financed principal = price − down − trade + trade debt − rebate + financed tax and fees.

The reverse calculation solves for a price consistent with the budget and entered tax policy. Percentage down payment is solved together with the price. Local tax treatment must be entered explicitly.

US state tax treatment and offer comparison: formula and assumptions

Taxable base = max(0, price + taxable fees − eligible trade deduction − eligible rebate); financing includes price, payoff, credits and financed costs.

Current scoped dealer-purchase rules for all 50 states and DC are available as source notes. A subset supports automatic base treatment; special or unresolved cases use an actual quoted tax amount. State choice does not determine a local rate.

Worked example

Reference example currency: USD. These fixed examples do not change with your calculator preferences.

Using the Compare offers example:

Vehicle price ($)

35000

Down payment ($)

5000

Cash rebate ($)

2000

Rate with rebate (%)

6

Promotional rate (%)

2

Loan term (years)

5

Compare down payment plus all scheduled payments under each offer.

Example result

These are illustrative inputs. Change the values to explore a different scenario.

What to keep in mind

Compare eligible rebate and promotional-rate offers using the same vehicle price, term, down payment, trade, debt payoff and fees. The promotional offer removes the manufacturer rebate and recalculates purchase tax, or uses your separate verified tax quotes.

Use scoped 2026 state taxable-base treatment, your verified base assumptions, or separate quoted taxes for the two offers. State selection does not guess a combined local tax rate.

The comparison includes entered cash costs and loan interest. Early payoff, future resale value and the opportunity cost of cash are outside the calculation.

Formula references

• CFPB: understanding mortgages (opens in a new tab)
• Investor.gov: financial tools and calculators (opens in a new tab)
• CFPB: comparing auto loans (opens in a new tab)

References explain the underlying methods; they do not imply endorsement or individual professional review of Finflo.

Common questions