Car Loan Payment Calculator With Interest Rate

A car loan payment calculator with an interest rate estimates your monthly principal-and-interest payment, plus the total interest over the loan term. Enter the amount borrowed, annual percentage rate (APR), and term to see the results; the estimate assumes a fixed rate and equal monthly payments.

Formula

The calculator uses the standard fixed-payment loan formula. It first calculates a monthly payment from the principal, monthly interest rate, and number of payments:

Payment = P × r ÷ [1 − (1 + r)⁻ⁿ]

• P is the amount borrowed, in dollars.
• APR is the annual percentage rate, entered as a percentage.
• r is the monthly rate, calculated as APR ÷ 1,200. For an 8% APR, r = 0.08 ÷ 12.
• n is the total number of monthly payments, calculated as loan term in years × 12.

The monthly payment is rounded to the nearest cent. Total interest is then calculated as the rounded monthly payment multiplied by the number of payments, minus the original principal: Total interest = payment × n − P. This means the total reflects the displayed payment amount.

Worked Example

Using the calculator’s default values—$20,000 borrowed, 8% APR, and a five-year term—the loan has 60 monthly payments. The monthly rate is 8 ÷ 1,200 = 0.0066667.

1. Calculate the rate factor: (1 + 0.0066667)⁻⁶⁰ ≈ 0.6712.
2. Calculate the payment: $20,000 × 0.0066667 ÷ (1 − 0.6712) ≈ $405.53 per month.
3. Calculate total paid using the rounded payment: $405.53 × 60 = $24,331.80.
4. Subtract the amount borrowed: $24,331.80 − $20,000 = $4,331.80 in total interest.

The resulting estimate is a monthly payment of $405.53 and total interest of $4,331.80. Small differences in intermediate decimal values do not change these cent-rounded results.

Assumptions

• The interest rate stays fixed for the full term.
• Payments are equal monthly installments, made at the end of each monthly period.
• Interest compounds monthly using the APR divided by 12.
• The calculation excludes fees, taxes, insurance, and other costs such as optional add-ons.

When to Use the Calculator

Use this estimate to understand how the borrowed amount, APR, and term affect a car loan’s scheduled payment and interest cost. It can help you compare hypothetical loan structures on the same assumptions, or check how a quoted payment relates to a stated amount, rate, and term. Enter the rate and terms supplied for the specific offer you are reviewing; do not treat the example defaults as a market quote.

The loan amount should represent the amount financed, not necessarily the vehicle’s advertised price. A down payment reduces the amount that must be borrowed. If a trade-in, taxes, fees, or optional products are included in the financing, they may increase the principal. Since this calculator has no separate fields for those items, include them in the loan amount only if they are actually financed and you want them represented in the estimate.

How the Rate and Term Change the Payment

For the same principal and term, a higher APR raises the monthly payment and total interest. A longer term usually lowers the required monthly payment, but it also means more payments accrue interest. These effects are connected: the payment alone does not show the full borrowing cost, so consider both displayed results when examining a loan’s arithmetic.

APR is entered as a percentage per year, not as a monthly percentage. The calculator converts it to a monthly rate by dividing by 12 and converting the percentage to a decimal; that is why the expression uses APR ÷ 1,200. Do not enter 0.08 for an 8% APR: enter 8. A 0.08 entry would mean 0.08% per year.

Reading Results and Common Misunderstandings

• Payment is not the full cost of owning a car. It covers only the modelled loan principal and interest. Insurance, fuel, maintenance, registration, and other ownership costs are outside the calculation.
• APR and the interest rate used in a contract may be presented differently. Use the APR specified for the calculation, and check the lender’s documents to understand how it is defined and which charges it incorporates.
• A quoted payment may include other items. If a lender’s figure includes financed products, fees, or a different payment schedule, it will not necessarily match this principal-and-interest estimate.
• Rounding matters over many payments. The calculator rounds the monthly amount to cents and uses that rounded amount to estimate total interest. A lender may adjust the final installment or apply payment dates and rounding according to its contract.

For the figures that apply to a particular offer, use the lender’s stated amount financed, APR, and term. If the payment schedule is not monthly, the rate changes during the loan, or the loan has a balloon payment, this formula does not represent that structure.

Limits of a Standard Payment Estimate

This formula assumes a fully amortizing loan: regular payments cover interest due and gradually repay principal until the balance reaches zero at the end of the term. It does not model variable rates, skipped or irregular payments, extra principal payments, late charges, or a final payment that differs from the others. It also cannot establish whether an application will be approved or what terms an applicant will receive.

To make an estimate more representative, check that the principal is the amount actually financed, the APR and term match the offer, and the payment frequency is monthly. Ask the lender for an itemized payment schedule if the disclosed payment differs, or if you need details about fees and other amounts outside the formula.

Frequently Asked Questions

How do I calculate a car payment with interest?
Convert the APR to a monthly decimal rate by dividing it by 1,200, multiply the amount borrowed by that rate, and divide by 1 − (1 + monthly rate)^{−number of monthly payments}. This calculator performs those steps and rounds the payment to cents.

Does a longer car loan term reduce the monthly payment?
For the same principal and APR, extending the term generally reduces the scheduled monthly payment because the balance is spread across more payments. The total interest can increase because interest is paid over a longer period.

Should I enter the car price or the amount financed?
Enter the amount borrowed. It may differ from the vehicle price after a down payment, trade-in, or financed charges. Use the figure shown as the amount financed in the relevant loan details.

Why is my lender’s payment different from the calculator?
The lender may use a different amount financed, APR, term, payment date, rounding method, or payment structure. The disclosed payment may also include amounts this calculator excludes. Compare the assumptions and request an itemized explanation if the difference is unclear.

Does the result include insurance and taxes?
No. It estimates principal and interest only. Insurance, taxes, fees, and other costs are not included unless they are part of the principal amount you enter.

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

Related

• Auto Loan Calculator With Trade-In and Amount Owed (Negative Equity)
• Car Loan Calculator With Down Payment: Monthly Car Payment

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