What Is My Car Payment? Estimate the Monthly Cost

This car payment calculator estimates the monthly principal-and-interest payment for a fixed-rate auto loan. Enter the amount borrowed, annual percentage rate (APR), and loan term to see the monthly payment and total interest; it does not calculate the full cost of owning or operating a car.

Formula

The calculator uses the standard amortizing-loan payment formula. It assumes equal monthly payments and a fixed rate throughout the term:

Payment = P × r ÷ [1 − (1 + r)⁻ⁿ]

• P is the loan principal, in dollars. It is the amount financed, not necessarily the vehicle’s sale price.
• r is the monthly interest rate, calculated as APR ÷ 1,200. For an 8% APR, r = 8 ÷ 1,200, or about 0.006667 per month.
• n is the number of monthly payments, calculated as the term in years × 12.

The payment is rounded to the nearest cent. Total interest is calculated as the rounded monthly payment × number of payments − principal. This is an estimate based on the inputs; a lender’s actual schedule can differ because of payment dates, rounding, fees, or other contract details.

Worked Example

Using the calculator’s defaults—$20,000 borrowed, 8% APR, and a five-year term:

1. Convert the APR to a monthly rate: 8 ÷ 1,200 = 0.0066667.
2. Convert the term to payments: 5 × 12 = 60 months.
3. Substitute into the formula: $20,000 × 0.0066667 ÷ [1 − (1.0066667)⁻⁶⁰].
4. The monthly payment is approximately $405.53 after rounding to cents.
5. Total paid using that rounded payment is $405.53 × 60 = $24,331.80. Estimated total interest is $24,331.80 − $20,000 = $4,331.80.

Assumptions

• The interest rate is fixed for the full loan term.
• Payments are equal, made monthly, and treated as end-of-period payments.
• Interest accrues monthly using the APR divided by 12; the APR is entered as a percentage per year.
• The estimate excludes fees, taxes, insurance, add-ons, and any separate charges. It does not include a down payment or trade-in unless those amounts have already been accounted for in the loan amount.

What a Car Payment Includes

In everyday use, “car payment” usually means the recurring amount due on an auto loan or lease. This calculator covers only a fixed-rate loan’s principal and interest. Principal repays the amount borrowed; interest is the cost of borrowing under the loan’s terms. A lease payment is calculated differently and is not represented by this formula.

Your actual monthly vehicle budget can also include costs that are not part of the loan payment, such as insurance, fuel, maintenance, parking, registration, or taxes. Some loan contracts may include financed charges or optional products in the amount borrowed. If they are financed, they increase the principal and therefore can increase the calculated payment. To model that effect, enter the total amount financed, not just the advertised vehicle price.

How to Choose Inputs and Read the Result

Use the amount you expect to borrow after accounting for any down payment, trade-in value, and amounts added to the financing. Enter the APR and term shown in the lender’s written offer or disclosure rather than assuming a rate or relying on a rough quote. The APR input is an annual percentage; the calculator converts it to a monthly rate internally. Entering 8 means 8%, not 0.08%.

The term should match the contract’s duration. A longer term spreads repayment over more months and can reduce the scheduled payment for the same principal and APR, while increasing the number of months interest can accrue. A shorter term changes both the payment and total interest. The calculator shows the mathematical result for the chosen inputs; it does not determine what payment is affordable, whether a lender will approve an application, or which contract to select.

• Payment: the estimated amount due each month for principal and interest.
• Total interest: estimated interest across the full term, using the rounded monthly payment.
• Total paid: not shown as a separate output, but it equals monthly payment × number of payments under this estimate.

Common Mistakes and Limits

A frequent mistake is using the car’s sticker price as the loan amount when the amount financed differs. A down payment generally reduces the amount borrowed; financed fees or add-ons may increase it. Another is comparing monthly payments without noting that the terms may have different lengths. A smaller payment alone does not tell you how much will be paid over the entire contract.

This formula models a level-payment, fixed-rate loan. It does not account for a variable rate, irregular payment dates, a balloon payment, skipped payments, late charges, or extra principal payments. It also assumes the APR can be treated as a monthly rate divided by 12. The lender’s payment schedule and contract disclosures are the sources for the exact figures. Values are rounded, so small differences can appear between an estimate and a statement.

Frequently Asked Questions

How do I calculate my car payment?
For a fixed-rate loan, use the principal, monthly rate (APR divided by 1,200), and total number of monthly payments in the amortizing-loan formula above. The calculator performs that calculation and rounds the payment to cents.

Does a car payment include insurance?
Not in this calculator. It estimates loan principal and interest only. Insurance and other costs of owning or operating a vehicle are separate unless a contract specifically includes a charge in the amount financed.

Should I enter the car price or the amount financed?
Enter the amount financed—the principal you expect to borrow. It may differ from the vehicle price after a down payment, trade-in, taxes, fees, or other items are accounted for.

Why does a longer loan term change the payment?
The same principal is divided across more scheduled payments, so the monthly amount can be lower. Interest is also calculated over a longer repayment period, which can raise total interest. The calculator compares only the inputs supplied.

Can I use this calculator for a lease?
No. Lease payments depend on factors such as the contract’s residual value and other lease-specific terms. This calculator uses a loan amortization formula and does not estimate a lease payment.

The result is an estimate, and 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 | $ | round(p * (apr / 1200) / (1 - (1 + apr / 1200) ^ -(yrs * 12)), 2) | 2
out int | Total interest | $ | pmt * yrs * 12 - p | 2