Quick answer
The total cost of each option = down payment + monthly payment × months. On a $30,000 car with a $3,000 down payment, a $2,500 rebate at 6.5% costs $31,762.24 in total, while the 1.9% promotional rate costs $31,324.16, so the low rate is $438.08 cheaper.
Enter price, down payment, rebate, both rates and the term. The calculator returns the total cost of each option and the better choice. Use this cash back or low interest calculator to check your own figures.
Related tools: Interest Rate Calculator: Annual interest rate implied by a loan amount, payment and term. Cash Back Calculator: Cash back earned on card spending. Auto Loan Calculator: Monthly car payment after down payment and trade-in.
How to use the Cash Back or Low Interest Calculator
- Enter price ($) (above 0).
- Enter down payment ($) (0 or more).
- Enter cash rebate ($) (0 or more).
- Enter rate if you take the rebate (%) (between 0 and 100).
- Enter low promotional rate (%) (between 0 and 100).
- Enter term (months) (a whole number, between 1 and 120).
- Press Calculate to see the result, and use Reset to start again.
| Input | What to enter | Allowed values |
|---|---|---|
| Price | A number, in $ | > 0 |
| Down payment | A number, in $ | ≥ 0 |
| Cash rebate | A number, in $ | ≥ 0 |
| Rate if you take the rebate | A number, in % | ≥ 0, ≤ 100 |
| Low promotional rate | A number, in % | ≥ 0, ≤ 100 |
| Term | A whole number, in months | ≥ 1, ≤ 120 |
Formula and method
Formula
total cost = down payment + monthly payment × months
IEEE-754 double precision; money shown to cents, rates to 4 decimals. Results are estimates, not financial advice.
The rebate reduces the amount financed in the first option; the second option finances the full price at the low rate.
Worked examples
These examples are verified: each one is an automated test case that the live calculator must reproduce exactly.
Example 1
Inputs: Price = 30000; Down payment = 3000; Cash rebate = 2500; Rate if you take the rebate = 6.5; Low promotional rate = 1.9; Term = 60.
| Result | Value |
|---|---|
| Better choice | Take the low rate |
| Total cost with rebate | $31,762.24 |
| Total cost with low rate | $31,324.16 |
| Difference | $438.08 |
Example 2
Inputs: Price = 25000; Down payment = 0; Cash rebate = 1000; Rate if you take the rebate = 4; Low promotional rate = 3; Term = 48.
| Result | Value |
|---|---|
| Better choice | Take the rebate |
| Total cost with rebate | $26,011.07 |
| Total cost with low rate | $26,561.19 |
| Difference | $550.12 |
The first line is the headline result (better choice). Below it the cash Back or Low Interest Calculator lists total cost with rebate, total cost with low rate and difference, which describe the same case from other angles. IEEE-754 double precision; money shown to cents, rates to 4 decimals. Results are estimates, not financial advice.
How the comparison works
Taking the rebate reduces the amount financed ($24,500) at the higher 6.5% rate. Taking the low rate finances $27,000 at 1.9%. The totals include the down payment, so they compare like with like.
The result flips with the numbers
A larger rebate or a shorter term tilts the answer toward the rebate; a bigger loan or longer term favours the low rate. Run the numbers for your own offers. Rebate and down payment must be below the price.
How the result changes with price
Holding every other input at the first worked example, this table changes only price. It shows how sensitive the answer is to that one value; each row was produced by running this calculator.
| Price | Better choice | Total cost with rebate | Total cost with low rate |
|---|---|---|---|
| 15000 | Take the rebate | $14,152.70 | $15,588.51 |
| 30000 | Take the low rate | $31,762.24 | $31,324.16 |
| 60000 | Take the low rate | $66,981.30 | $62,795.44 |
| 120000 | Take the low rate | $137,419.44 | $125,738.01 |
What happens with invalid input
These messages are produced by the calculator itself, so you know what to fix.
- Down payment: entering "100" shows "The down payment must be less than the price." beside that field and no result.
- Cash rebate: entering "1000" shows "The rebate and down payment must be less than the price." beside that field and no result.
Choosing between the Cash Back or Low Interest Calculator and similar calculators
Each row shows what a related calculator on this site asks for and what it returns, so you can pick the one that matches your question.
| Calculator | You enter | It returns |
|---|---|---|
| [Interest Rate Calculator](/finance/interest-rate-calculator/) | loan amount, monthly payment and term | Interest rate (APR) |
| [Cash Back Calculator](/finance/cash-back/) | spending per month and cash back rate | Cash back per month |
| [Auto Loan Calculator](/finance/auto-loan-calculator/) | vehicle price, down payment and interest rate | Monthly payment |
| [Amortization Calculator](/finance/amortization-calculator/) | loan amount, interest rate and term | Monthly payment |
| [Loan Calculator](/finance/loan-calculator/) | loan amount, interest rate and term | Monthly payment |
Background: loans and mortgages
The interest rate is the cost of borrowing the principal; the APR also folds in certain fees, so a lower rate with high fees can have a worse APR. These calculators use the rate you enter and do not add fees, insurance or taxes, so add fees to the principal if you want to include them.
A fixed-rate loan is paid in equal instalments, early ones mostly interest. Extra payments go straight to principal, which shortens the loan and cuts interest; adjustable rates, escrow changes and prepayment penalties are not modelled.
Assumptions and limitations
- Rebate and down payment must be below the price
Results are estimates for planning, not financial advice. Lender terms, fees, taxes and rounding rules can change real figures, so confirm important numbers with your lender or a licensed adviser.
If a required value is empty, not a number, or outside its allowed range, the form marks that field with a message and shows no result instead of a misleading number. The automated checks deliberately try invalid entries for down payment and cash rebate to confirm this.
Frequently asked questions
Can I get both?
Usually the offers are alternatives.
Does the term matter?
Yes, longer terms favour the low rate.
What about taxes and fees?
They are not included.
What does the Cash Back or Low Interest Calculator calculate?
Compare a cash rebate with a lower financing rate on a purchase. It returns Better choice, Total cost with rebate, Total cost with low rate and Difference.
What formula does the Cash Back or Low Interest Calculator use?
total cost = down payment + monthly payment × months. The rebate reduces the amount financed in the first option; the second option finances the full price at the low rate.
What do I need to enter in the cash Back or Low Interest Calculator?
You enter Price ($), Down payment ($), Cash rebate ($), Rate if you take the rebate (%), Low promotional rate (%) and Term (months).
How is the result rounded or limited?
IEEE-754 double precision; money shown to cents, rates to 4 decimals. Results are estimates, not financial advice. Rebate and down payment must be below the price.
What is an example of a cash Back or Low Interest result?
With price 30000, down payment 3000, cash rebate 2500, rate if you take the rebate 6.5 and low promotional rate 1.9, the better choice is Take the low rate.
Can I rely on this calculator for a decision?
Results are estimates for planning, not financial advice. Lender terms, fees, taxes and rounding rules can change real figures, so confirm important numbers with your lender or a licensed adviser. For this calculator in particular: Rebate and down payment must be below the price.
Related calculators
- Interest Rate Calculator — Annual interest rate implied by a loan amount, payment and term.
- Cash Back Calculator — Cash back earned on card spending.
- Auto Loan Calculator — Monthly car payment after down payment and trade-in.
- Amortization Calculator — Full amortization schedule with optional extra monthly payments.
- Loan Calculator — Estimate your monthly loan payment, total interest and total cost.
- HELOC Calculator — Interest-only draw-period payment and the repayment-period payment of a home equity line.
- Credit Card Interest Calculator — Interest charged on a card balance for a billing period.
Sources
- Standard time-value-of-money relations (e.g. Brealey, Myers & Allen, Principles of Corporate Finance)
Content last reviewed 2026-11-04. Formulas and worked examples are checked by automated tests against independently computed values.