The price on the windshield is not always the amount you end up financing. Your down payment, trade-in, taxes, fees, and loan term can all change the final payment.
This calculator helps you see what those choices do to the monthly payment and total interest. It also lets you test extra payments before you sign a financing agreement.
The most useful comparison is not just one payment against another. Look at how much you are borrowing, how long you will owe it, and what the loan costs in total.
Start With the Amount You’re Actually Financing
The sticker price is not always the number that belongs in an auto loan calculator. The important number is the amount financed, which is what you actually borrow.
A down payment is money you pay upfront instead of borrowing. A trade-in is a vehicle you give the dealer for credit toward another vehicle.
Taxes and dealer fees can also become part of the loan when you finance them. The calculator should receive the final amount you expect the lender to finance.
Suppose a vehicle costs $35,000 and you put $5,000 down. Before any trade-in, taxes, or financed fees, the amount financed would be $30,000.
Trade-Ins Can Reduce or Increase the Balance
A trade-in does not automatically lower the new loan by its full value. Positive equity means your vehicle is worth more than the amount you still owe. Negative equity means you owe more than the vehicle is worth.
Suppose your trade-in is worth $12,000 and you owe $7,000. You have $5,000 of positive equity that can reduce the amount financed.
Now reverse the numbers. If the vehicle is worth $12,000 and you owe $15,000, you have $3,000 of negative equity.
If that $3,000 is added to a new $30,000 loan, the amount financed becomes $33,000. At the same illustrative rate and term, the payment rises with it.
Why the Loan Term Can Be Deceptive
A loan term is the number of months allowed for repayment. Longer terms usually lower the required payment because the same balance is spread across more months. That can make a vehicle look easier to afford without making the financing cheaper.
Here is the same $30,000 loan at an illustrative 7% rate with three different terms:
| Loan term | Monthly payment | Total interest | Total paid |
|---|---|---|---|
| 48 months | $718.39 | $4,482.59 | $34,482.59 |
| 60 months | $594.04 | $5,642.16 | $35,642.16 |
| 72 months | $511.47 | $6,825.85 | $36,825.85 |
The 7% rate is only an example, not a current market rate. Moving from 60 months to 72 months lowers the payment by about $83. Total interest rises by about $1,184.
Moving from 60 months to 48 months raises the payment by about $124. Total interest falls by about $1,160.
How New or Used Changes the Starting Rate
The calculator asks whether the vehicle is new or used because that choice affects its starting rate estimate. A credit score is a number lenders may use to estimate lending risk. A credit tier groups a range of credit scores.
The calculator combines the new-or-used selection with your credit tier to choose a starting rate from its current rate data. That starting rate is for planning. It is not a lender offer, and you can replace it with the interest rate you are actually quoted.
What a Down Payment Changes
A larger down payment reduces the amount you need to finance. Using the same 60-month, 7% example, financing $25,000 instead of $30,000 drops the payment from $594.04 to $495.03.
That is about $99 less each month. Total interest also falls from $5,642.16 to $4,701.80.
The calculator does not ask for the down payment separately. Account for it before entering the amount financed.
How Taxes and Dealer Fees Affect the Loan
Sales tax, title charges, registration costs, and dealer fees can change the amount you need to borrow. A dealer fee is a charge added by the dealership for certain services or transactions.
If you pay a cost upfront, it does not increase the loan balance. If you finance it, you pay interest on that cost along with the vehicle.
For example, adding $2,000 of financed costs to the $30,000 example creates a $32,000 balance. At 7% for 60 months, the payment becomes $633.64. Total interest becomes $6,018.30.
How the Calculator Turns the Balance Into a Payment
Most auto loans use amortization. Amortization is the process of paying down a loan through scheduled payments over time.
Principal is the unpaid amount borrowed. Interest is the amount the lender charges for borrowing that principal. For a fixed-rate loan, the calculator uses the amount financed, monthly interest rate, and number of payments to find one scheduled monthly payment.
The standard formula is:
M = P × [r(1 + r)ⁿ] ÷ [(1 + r)ⁿ − 1]
In the formula:
- M: The required monthly payment.
- P: The original amount financed.
- r: The monthly interest rate.
- n: The total number of monthly payments.
The monthly interest rate is the annual interest rate divided by 12. Suppose you finance $30,000 for 60 months at the illustrative 7% rate. The required principal-and-interest payment is $594.04.
Across all 60 scheduled payments, you pay about $5,642 in interest and $35,642 in total.
What Extra Payments Can Change
The calculator also lets you add an optional extra monthly payment. An extra payment can reduce principal faster when the lender applies it directly to the balance.
Add $100 each month to the $30,000 example and the displayed payment becomes $694.04. The required scheduled payment itself remains $594.04.
The loan is paid off during month 50 instead of month 60. Total interest falls to about $4,670, saving roughly $972. Check how your lender applies extra payments before relying on that result.
Why APR and Interest Rate Are Different
Interest rate and annual percentage rate are different measurements. The interest rate is the percentage charged on unpaid principal. Annual percentage rate, or APR, can also include certain lender fees.
APR is often higher when those additional costs are included. The figures can be equal when no additional costs are included in the APR calculation.
Use the loan’s interest rate in this calculator when you know it. APR is generally more useful when comparing the broader cost of competing auto loan offers.
What This Calculator Does Not Include
The calculator estimates principal and interest. It does not estimate the full monthly cost of owning the vehicle.
Insurance, registration, fuel, maintenance, repairs, parking, and other ownership expenses sit outside the displayed loan payment. Taxes and dealer fees appear only when you include them in the amount financed.
The calculator assumes equal monthly payments that begin one month from now. It also assumes a fixed interest rate for the full term.
Common Auto Financing Mistakes
The calculator works from whatever numbers you give it. The mistakes below usually involve the amount financed, the term, or the costs that sit outside the loan payment.
Using the Sticker Price as the Loan Balance
The advertised price can differ from the amount financed. Adjust for the down payment, trade-in position, and any costs being financed.
Ignoring the Loan on Your Trade-In
Subtract the amount you still owe from the vehicle’s trade-in value. A remaining loan balance can reduce your credit or create negative equity.
Choosing 72 or 84 Months Only for the Lower Payment
A longer term can lower the payment while increasing total interest. Compare both figures before deciding what feels affordable.
Financing Every Extra Cost
Adding taxes, fees, warranties, or other products to the loan increases the amount financed. You then pay interest on those financed costs.
Comparing Dealer Financing Without Another Quote
Dealer-arranged financing can differ from a rate offered directly by another lender. A preapproval is a lender’s conditional offer based on an initial review. Having one gives you another financing offer to compare at the dealership.
Frequently Asked Questions
These questions cover the parts of an auto loan estimate that are easiest to get wrong. Your lender’s paperwork should provide the final figures.
Should I enter the car price or amount financed?
Enter the amount you expect to borrow. Adjust the vehicle price for your down payment, trade-in position, and any taxes or fees you plan to finance.
Does a bigger down payment always lower the car payment?
Yes, when the interest rate and term stay the same. A larger down payment reduces the amount financed, which lowers the required payment.
What if I owe money on my trade-in?
Subtract the amount you owe from the trade-in value. Positive equity can reduce the new balance, while negative equity can increase it if rolled into the loan.
Is a 72-month loan cheaper than a 60-month loan?
Not necessarily. A 72-month loan can have a lower monthly payment but higher total interest when the amount financed and interest rate stay the same.
Does paying extra each month help?
It can. Extra principal payments can shorten the payoff period and reduce total interest when the lender applies them directly to principal.
Why does the calculator ask whether the car is new or used?
The selection helps set the calculator’s starting interest rate estimate. The calculator also uses your credit tier when choosing that starting rate.
Does the monthly payment include insurance?
No. The displayed payment covers principal and interest, including any optional extra payment you enter. Vehicle insurance and other ownership costs are separate.