Car Payment Schedule Calculator: Monthly Cost and Interest

A car payment schedule calculator estimates your fixed monthly loan payment and total interest from the amount financed, annual percentage rate (APR), and loan term. Enter those figures to see the payment and the interest cost across the scheduled term; the estimate assumes regular monthly payments and does not include ownership expenses.

Formula

The calculator uses the standard fixed-payment loan formula. It first finds the monthly payment, rounds that payment to cents, then estimates total interest by multiplying the rounded payment by the number of monthly payments and subtracting the original amount financed.

• Monthly payment: M = round(P × r / [1 − (1 + r)⁻ⁿ], 2)
• Total interest: I = M × n − P
• Monthly rate: r = APR / 1,200

P is the amount financed in dollars; APR is the annual percentage rate entered as a percentage; r is the monthly rate as a decimal; n is the term in months, calculated as years × 12; M is the monthly payment in dollars; and I is estimated total interest in dollars. For example, an APR of 8% becomes 0.08 / 12, or about 0.006667 per month.

Worked Example

Using the calculator’s default values—$20,000 financed, 8% APR, and five years—the scheduled term is 5 × 12 = 60 monthly payments. The monthly rate is 8 / 1,200 = 0.0066667.

1. Payment before rounding = 20,000 × 0.0066667 / [1 − (1 + 0.0066667)⁻⁶⁰].
2. Rounded monthly payment = $405.53.
3. Total of scheduled payments = $405.53 × 60 = $24,331.80.
4. Estimated total interest = $24,331.80 − $20,000 = $4,331.80.

The result uses the rounded monthly payment for the interest total, as the calculator formula specifies. A lender’s actual final payment can differ by a small amount because payment dates, daily interest calculations, and rounding practices may vary.

Assumptions

• The APR and scheduled payment remain fixed for the full term.
• Payments are made monthly at the end of each period.
• Interest is compounded monthly using APR divided by 12.
• The calculation excludes fees, taxes, insurance, optional products, and other costs unless they are included in the amount financed.

What a Car Payment Schedule Shows

A payment schedule, often called an amortization schedule, describes how a fixed installment loan is paid down over time. Each payment covers interest accrued for the period and reduces the remaining principal. Early in a level-payment loan, interest generally makes up a larger share of the payment because the balance is higher. As the principal falls, the interest portion usually declines and more of each payment goes toward principal.

This calculator reports the regular monthly payment and total interest for the full schedule. It does not display each month’s principal-and-interest split or the outstanding balance after a particular payment. Those figures require a period-by-period amortization calculation. The stated total interest is an estimate over the original schedule, not a quote or payoff amount for a specific date.

What to Enter and How to Read the Results

• Amount financed: Enter the amount borrowed, not automatically the vehicle’s advertised price. A down payment or trade-in may reduce the amount financed; financed add-ons or other amounts may increase it. Use the figure in the lender’s loan disclosure when available.
• APR: Enter the annual percentage rate as a percent, such as 8 for 8%. Do not enter 0.08, which would mean 0.08% in this field. Get the actual APR and any financed charges from the lender.
• Term: Enter the number of years in the loan term. The calculator converts years to monthly payments, so a five-year term means 60 scheduled payments.

The first result is the estimated amount due each month for principal and interest under the formula. Total interest is the estimated financing cost over the complete schedule. It is separate from the total payments: the latter includes repayment of principal as well as interest. The total does not represent the full cost of owning or operating a vehicle.

Factors That Change the Schedule

For the same amount financed, a higher APR generally increases both the scheduled payment and total interest. A longer term can lower the required monthly payment while increasing the number of periods over which interest accrues. These are mathematical effects, not a recommendation about which term or rate to choose. Use the terms and figures actually presented for the loan you are evaluating.

Down payment and trade-in equity affect the schedule only insofar as they change the amount financed. Vehicle price alone is not enough to calculate a payment if the amount borrowed, APR, or term is unknown. Taxes, registration charges, insurance, maintenance, fuel, and other ownership costs are not calculated here. Some may be paid separately, while some charges may be included in a financed balance; check the loan documents to see what the amount financed contains.

Common Calculation Mistakes and Limits

• Mixing up APR and monthly rate: Enter APR as a yearly percentage. The calculator divides it by 1,200 to produce the monthly decimal rate.
• Using the vehicle price instead of the loan amount: The formula needs the principal actually financed. Subtract any amount paid up front and account for amounts added to the loan where applicable.
• Assuming every month has identical real-world timing: The formula models regular monthly periods. A lender may calculate interest using actual dates or other contract details, so the precise schedule can differ.
• Ignoring rounding: The payment is rounded to the nearest cent before total interest is calculated. Lenders may make a small adjustment to a final installment to clear the remaining balance.

The calculator is for fixed-rate, level-payment arithmetic. It does not model variable rates, skipped or late payments, extra principal payments, payment-date changes, refinancing, fees paid separately, or a payoff before the end of the term. For an exact payment breakdown or payoff figure, use the schedule and terms supplied by the lender.

Frequently Asked Questions

How do I calculate a car payment?
Use the amount financed, monthly interest rate (APR divided by 1,200), and number of monthly payments in the fixed-payment formula. This calculator applies that formula and rounds the monthly result to cents.

Does the car payment include insurance and taxes?
No. The calculated payment covers modeled principal and interest only. Insurance and other vehicle expenses are outside the formula unless a particular cost is included in the loan amount you enter.

Why is my lender’s payment different?
The lender may use a different financed amount, exact payment dates, contract-specific interest calculations, fees, or rounding. Compare the amount financed, APR, and term in the loan documents with the inputs used here.

Does a longer car loan reduce total interest?
Not necessarily. A longer term means more scheduled payments; with the same principal and APR, it commonly lowers the monthly payment but raises total interest because interest accrues over more periods.

Can I use this calculator for a lease?
No. A lease payment can depend on factors such as the vehicle’s residual value, fees, and lease-specific terms. This formula models a fixed-payment loan that repays principal and interest.

This result is an estimate for education, 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