New Car Loan Calculator: Monthly Payment Estimate

A new car loan calculator estimates your monthly principal-and-interest payment from the amount borrowed, annual percentage rate (APR), and loan term. Enter those figures to see the payment and estimated total interest; the result is a calculation, not a lender quote.

Formula

The calculator uses the standard fixed-payment loan formula. It converts the annual APR to a monthly rate, then calculates the level monthly payment needed to repay the principal and interest over the term:

Payment = P × r ÷ [1 − (1 + r)⁻ⁿ]

• P is the amount financed, in dollars.
• r is the monthly interest rate as a decimal: APR in percent ÷ 1,200.
• n is the number of monthly payments: loan term in years × 12.
• Payment is the estimated monthly principal-and-interest amount, in dollars.

For the second result, estimated total interest equals the monthly payment multiplied by the number of payments, minus the amount borrowed. The payment formula assumes the same payment amount each month and a fixed rate. The calculator displays the monthly payment to the nearest cent and uses that rounded amount to estimate total interest.

Worked Example

Using the default inputs—$20,000 financed, 8% APR, and a five-year term—the monthly rate is 8 ÷ 1,200 = 0.0066667, and the term is 5 × 12 = 60 payments.

Payment = 20,000 × 0.0066667 ÷ [1 − (1 + 0.0066667)⁻⁶⁰] = $405.53 per month when rounded to the cent.

Estimated total interest = $405.53 × 60 − $20,000 = $4,331.80. The estimated total of the scheduled payments is $24,331.80, including the original amount financed.

Assumptions

• The APR is fixed for the full loan term.
• Payments are equal monthly payments, made at the end of each monthly period.
• Interest is modelled monthly at APR ÷ 12.
• The calculation does not include taxes, registration, insurance, fees, optional products, or a down payment unless those amounts have already been reflected in the loan amount entered.

What to Enter for a New Car

The loan amount is the amount actually financed, not necessarily the vehicle’s advertised price. A down payment or trade-in equity can reduce how much is borrowed; taxes and other charges added to the contract can increase it. Use the figures supplied for the specific vehicle and proposed transaction rather than assuming the calculator knows those amounts.

• Loan amount: enter the principal you expect to finance. If you are comparing possible transaction totals, calculate each amount separately.
• APR: enter the annual percentage rate provided for the loan scenario. APR may reflect certain borrowing costs, but this calculator uses it only as the annual rate input in the payment formula. Ask the lender which figures are included in its quoted APR and payment.
• Term: enter the repayment period in years. The formula converts it to a whole number of monthly periods. A term entered as a fraction of a year is also converted to months by the calculator.

The default values are illustrative inputs, not a claim about available rates or loan terms. Replace them with figures from a lender’s written estimate or disclosure. Rates, fees, and loan conditions depend on the particular transaction and are not determined by this calculator.

How to Read the Payment

The monthly result covers modeled principal and interest only. It is not necessarily the full monthly cost of owning or operating a car. Insurance, fuel, maintenance, parking, and other ownership costs are outside the formula. Some transaction charges may be paid separately, while others may be financed; the effect on this estimate depends on whether they are included in the loan amount.

Total interest is an estimate across all scheduled payments, not an extra monthly charge to add to the displayed payment. With the example inputs, multiplying the cent-rounded payment by 60 gives $24,331.80 in scheduled payments; subtracting the $20,000 principal gives $4,331.80 in modeled interest. Actual account totals can differ if payment dates, amounts, rates, or loan terms differ from these assumptions.

Comparing Scenarios and Common Errors

To understand how different inputs affect the estimate, change one input at a time and note the result. A larger amount financed generally increases the payment when the rate and term are unchanged. A longer term spreads repayment across more months and can lower the scheduled payment, while the number of interest-accruing periods also increases. The exact effects depend on the entered APR and principal.

• Do not enter a monthly rate as the APR. The calculator expects an annual rate in percent, such as 8 for 8%, and converts it to a monthly rate.
• Do not enter the vehicle price as the loan amount if the amount financed will differ because of a down payment, trade-in, or financed charges.
• Do not treat the payment as an all-in vehicle budget. It excludes ownership costs and any contract items not included in the principal.
• Do not expect an exact match to a lender’s schedule when the lender uses different payment dates, rate conventions, fees, or rounding.

This calculator is for a fixed-rate loan with regular level payments. It does not model a variable rate, skipped or irregular payments, extra principal payments, a balloon payment, or changes to the balance during the term. The formula also does not determine whether a lender will offer the entered terms.

Frequently Asked Questions

How do I calculate a new car loan payment?
Enter the amount financed, APR, and repayment term. The calculator converts APR to a monthly rate and applies the fixed-payment formula to estimate the monthly principal-and-interest payment.

Does the monthly payment include tax and insurance?
No. The result covers only the loan payment calculated from principal, APR, and term. Taxes or fees affect it only if they are included in the loan amount; insurance is not modeled.

Is the calculator’s payment guaranteed to match a lender’s quote?
No. It is an estimate based on the inputs and assumptions shown. A lender’s payment may differ because of contract details, fees, payment timing, or rounding.

Why can a longer loan term reduce the monthly payment?
The same principal is divided across more monthly payments. However, interest is modeled over more periods, so total interest may be higher than for a shorter term with the same principal and APR.

Should I enter the car’s price or the amount financed?
Enter the amount financed. It can differ from the price after a down payment, trade-in value, taxes, and other charges are accounted for. Use the transaction figures that apply to your estimate.

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

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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