Monthly Payment on a New Car: Estimate the Cost

This calculator estimates the monthly principal-and-interest payment on a car loan when you enter the amount borrowed, annual percentage rate (APR), and loan term. It also shows the total interest over the term; the estimate excludes vehicle taxes, fees, insurance, and other costs that may affect a real payment.

Formula

The calculator uses the standard fixed-payment loan formula. Monthly payment = loan principal × monthly interest rate ÷ [1 − (1 + monthly interest rate)^{−number of monthly payments}]. In symbols, M = P × r / [1 − (1 + r)⁻ⁿ], where:

• M is the monthly principal-and-interest payment in dollars.
• P is the amount financed in dollars.
• r is the monthly interest rate as a decimal, calculated as APR ÷ 1,200. For example, 8% APR gives 0.006667 per month.
• n is the total number of monthly payments, calculated as loan term in years × 12.

The displayed payment is rounded to cents. Total interest is calculated as the displayed monthly payment × number of payments − principal. The model assumes a level payment and a fixed rate throughout the term.

Worked Example

Using the calculator’s default inputs—$20,000 financed, 8% APR, and 5 years—the calculation is:

1. Convert APR to a monthly decimal rate: 8 ÷ 1,200 = 0.0066667.
2. Convert the term to payments: 5 × 12 = 60.
3. Substitute into the payment formula: $20,000 × 0.0066667 ÷ [1 − (1.0066667)⁻⁶⁰].
4. The monthly principal-and-interest payment is $405.53.
5. Total interest using the rounded payment is $405.53 × 60 − $20,000 = $4,331.80.

Assumptions

• The APR is fixed for the entire loan term.
• Payments are equal, made monthly, with the first payment one month after borrowing.
• Interest is modelled as monthly compounding at APR ÷ 12.
• The estimate excludes taxes, title and registration charges, dealer or lender fees, insurance, maintenance, and any add-ons. It does not model a down payment or trade-in separately; subtract those amounts from the vehicle’s price when determining the amount financed.

What Determines a New-Car Payment?

The amount financed, APR, and term work together. A larger loan balance raises the payment. A higher APR also raises it because more interest accrues on the unpaid balance. A longer term generally lowers the required monthly payment by spreading repayment over more months, but it usually increases the total interest paid when the rate and principal are otherwise unchanged.

For a car purchase, the loan amount is not necessarily the advertised vehicle price. A useful starting calculation is the agreed vehicle price plus any costs included in the loan, minus the down payment and trade-in credit. A balance rolled over from an earlier vehicle loan can increase the new amount financed. To estimate the payment accurately, use the amount the lender will actually finance—not simply the sticker price.

Reading the Estimate and Comparing Scenarios

The first output is the scheduled monthly payment for principal and interest. It is not necessarily the complete amount due each month: insurance is commonly paid separately, while some taxes, fees, or optional products may be included in financing or billed another way. The calculator’s total interest is the sum implied by its rounded monthly payment, not the total cash cost of owning the car.

To understand how loan structure changes the result, hold two inputs constant while changing the third. For example, compare the payment and interest outputs for two terms using the same amount and APR. A longer term can make the monthly figure smaller without making the vehicle less expensive; the balance can also take longer to decline. Compare the amount financed, APR, number of payments, and any separately disclosed charges—not just the monthly payment.

The sample calculation is only an illustration, not a claim about current borrowing rates. Enter the APR and financed amount shown in the lender’s actual offer or disclosure. If a quoted rate is not expressed as APR, or if the contract uses a different payment schedule, the calculator’s result may not match the contract.

Common Sources of a Different Payment

• Down payment and trade-in: These can reduce the amount borrowed, but an unpaid balance from a trade-in may add to it.
• Taxes and fees: The result changes if these are financed, even though this calculator does not itemize them.
• Optional products: Products included in the contract can increase the principal and payment.
• Rounding and dates: This estimate rounds the monthly payment to cents and assumes regular monthly periods. A lender’s payment schedule, first-payment date, or rounding method can produce a small difference.
• APR versus interest rate: APR is a standardized annualized cost measure, while the contract’s interest calculation and included charges determine the actual schedule. Do not substitute a different quoted rate without checking what it represents.

A frequent misconception is that a lower payment automatically means a lower-cost loan. It may instead reflect a longer repayment period. Look at the total number of payments and total interest as well as the monthly amount.

Frequently Asked Questions

How do I calculate a monthly payment on a new car?
Use the amount financed, APR, and number of monthly payments in the fixed-payment formula shown above. This calculator converts annual APR to a monthly rate and estimates the principal-and-interest payment.

Does a car payment include insurance and taxes?
Not in this calculator. It estimates principal and interest only. Taxes, insurance, registration charges, and other costs may be separate or included in a loan or payment arrangement, so check the itemized figures you receive.

How does a down payment change the monthly payment?
A down payment generally reduces the amount financed if the other inputs stay the same. Enter the resulting financed balance as the loan amount to estimate the payment; account for any trade-in balance or costs added to the loan.

Will a longer car loan lower the monthly payment?
With principal and APR unchanged, extending the term generally reduces each scheduled payment because repayment is spread over more months. It also means more payments and can result in more total interest.

Why is my lender’s payment different from this estimate?
The financed amount, APR, term, fees, add-ons, first-payment timing, or rounding may differ from the inputs or assumptions here. Compare the calculator inputs with the lender’s itemized disclosure and payment schedule.

This result is an estimate, and the lender’s disclosure gives the exact figures.

Related

• Calculate My New Car Payment? Estimate It Here
• Calculate a New Car Loan Payment
• Behind on Car Payments? Estimate Your Payment Options

in p | Loan amount | $ | 20000 | 1 | 100000000
in apr | Interest rate (APR) | % | 8 | 0.01 | 100
in yrs | Loan term | years | 5 | 0.0833 | 50
out pmt | Monthly payment | $ | p * (apr / 1200) / (1 - (1 + apr / 1200) ^ -(yrs * 12)) | 2
out int | Total interest | $ | pmt * yrs * 12 - p | 2