American Financial Car Payment Calculator

This American financial car payment calculator estimates the monthly principal-and-interest payment on a fixed-rate auto loan from the amount borrowed, APR and term. Enter those three figures to see the monthly payment and estimated total interest; use your lender’s quoted terms for a personalized figure.

Formula

The calculator uses the standard fixed-payment loan formula. It first calculates the payment that repays the principal and interest over the stated number of monthly payments, then estimates total interest by subtracting the amount borrowed from the sum of those rounded payments.

Monthly payment: M = round[P × r / (1 − (1 + r)⁻ⁿ), 2], where r = APR / 1200 and n = 12 × t.

• M is the monthly payment in dollars.
• P is the loan principal in dollars.
• APR is the annual percentage rate entered as a percentage, such as 8 for 8%.
• r is the monthly rate as a decimal.
• t is the term in years; n is the number of monthly payments.

Total interest: I = M × n − P, where I is estimated interest in dollars. The payment is rounded to cents before total interest is calculated, matching the way the calculator presents its results.

Worked Example

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

1. Convert APR to a monthly decimal rate: r = 8 / 1200 = 0.0066667.
2. Convert the term to payments: n = 5 × 12 = 60 months.
3. Substitute into the payment formula: M = round[20,000 × 0.0066667 / (1 − (1 + 0.0066667)⁻⁶⁰), 2] = $405.53 per month.
4. Calculate total interest using the rounded payment: I = $405.53 × 60 − $20,000 = $4,331.80.

This is a mathematical estimate based on level monthly payments. A lender’s payment schedule may differ because of actual loan terms, payment dates, fees or other amounts included in the financing.

Assumptions

• The interest rate is fixed for the entire term.
• Payments are equal, made monthly, and assumed to occur at the end of each monthly period.
• Interest is modelled monthly at APR divided by 12.
• The calculation excludes taxes, title and registration charges, dealer or lender fees, insurance, add-on products and any down payment or trade-in unless already reflected in the loan amount.

What an Auto Loan Payment Includes

A vehicle payment can mean more than the principal-and-interest amount calculated here. The principal is the money financed to purchase the car, while interest is the borrowing cost represented by the APR input. Depending on the transaction, the amount financed may include eligible charges or products. A down payment or trade-in can reduce the principal, but this calculator does not ask for those separately: enter the amount that will actually be financed.

Recurring costs such as insurance, fuel, maintenance and some ownership charges are not part of this loan formula. They can materially affect the overall cost of owning a vehicle, so a monthly payment should not be mistaken for a complete vehicle budget. The calculation also does not determine whether a lender will approve an application or what rate or fees may apply.

How to Use the Estimate

• Loan amount: Enter the principal shown in the proposed financing details, not necessarily the car’s advertised price.
• APR: Enter the annual percentage rate as a percentage. For example, type 8 for 8%, not 0.08.
• Term: Enter the loan duration in years. The calculator converts it to monthly payments.
• Review both outputs: The payment is a monthly amount; total interest is the estimated interest over the full scheduled term.

For a simple comparison, change one input at a time while holding the others constant. A longer term spreads repayment across more months and can lower the calculated monthly payment, but it also means more scheduled payments. The resulting total-interest figure helps show that trade-off under the entered assumptions; it does not include other costs or predict future changes to a contract.

Common Misunderstandings and Limits

APR is not the monthly rate. The calculator divides the annual percentage by 12 and then by 100 to obtain a monthly decimal rate. Entering 0.08 when the intended APR is 8% would instead represent 0.08%, producing a very different result.

The loan amount is not always the vehicle price. Amount financed may differ after a down payment, trade-in, taxes, fees or products are considered. Use the actual principal from the financing disclosure when available. Do not add an item twice if it is already included in that principal.

Rounding affects totals. Monthly payments are rounded to the nearest cent in this estimate, and total interest uses that rounded payment multiplied by the number of months. A real amortization schedule may adjust the final payment to settle a small remaining balance.

This calculator models a fixed-rate, fully amortizing loan with regular monthly payments. It does not model irregular payment dates, skipped or late payments, extra principal payments, variable rates, balloon payments, payoff quotes, fees financed separately or a changing balance. For exact amounts and the payment schedule, consult the lender’s written disclosure and contract.

Frequently Asked Questions

How much is a $20,000 car payment over five years?
At the calculator’s default 8% APR, the estimated principal-and-interest payment is $405.53 per month, with estimated total interest of $4,331.80. A different APR or financed amount changes the result.

Does this calculator include a down payment?
No separate down-payment field is included. Subtract any down payment or applicable trade-in value when determining the principal you enter, and use the financing documents to confirm the amount financed.

Why does a longer car-loan term reduce the monthly payment?
The principal is divided across more scheduled payments, which can reduce each payment. Interest accrues over the longer repayment period, so total interest can rise even when the monthly amount is lower.

Is APR entered as 8 or 0.08?
Enter 8 for an APR of 8%. The calculator converts the percentage to a monthly decimal rate internally.

Why is my lender’s payment different?
The lender may use a different financed amount, rate, payment timing or rounding method, or include charges not represented by this calculator. Compare the inputs and review the lender’s disclosure for the exact schedule.

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

Related

• Daily Loan Amortization Schedule Calculator
• Loan Amortization: How Payments Reduce Your Balance
• Create a Loan Amortization Schedule

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