Estimate Car Payment: Monthly Cost and Interest

This car payment calculator estimates your monthly principal-and-interest payment from the amount financed, APR, and loan term; it also estimates total interest using the rounded monthly payment. Enter the figures from a lender’s quote or use the defaults to see how the calculation works.

Formula

The calculator uses the standard fixed-payment loan formula. It converts the annual percentage rate (APR) to a monthly rate, then calculates a level payment that pays down the balance over the selected number of months:

Monthly payment = P × r ÷ [1 − (1 + r)⁻ⁿ]

• P is the amount financed, in dollars.
• r is the monthly interest rate, calculated as APR ÷ 1,200 when APR is entered as a percentage.
• n is the number of monthly payments, calculated as years × 12.

Total interest is calculated as the displayed monthly payment multiplied by the number of payments, minus the original amount financed. Because the monthly payment is rounded to cents before this total is calculated, the displayed interest reflects that rounded payment.

Worked Example

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

1. Convert APR to a monthly rate: 8 ÷ 1,200 = 0.0066667.
2. Calculate the number of payments: 5 × 12 = 60.
3. Apply the payment formula: $20,000 × 0.0066667 ÷ [1 − (1.0066667)⁻⁶⁰] = $405.53 per month, rounded to cents.
4. Calculate total interest using the rounded payment: ($405.53 × 60) − $20,000 = $4,331.80.

The estimate is therefore $405.53 per month, with $4,331.80 in total interest under these assumptions. A lender’s figures can differ if its APR, financed amount, payment schedule, or rounding method differs.

Assumptions

• The interest rate is fixed for the full term.
• Payments are equal monthly payments made at the end of each monthly period.
• Interest accrues monthly at APR ÷ 12.
• The estimate excludes sales or other taxes, registration, fees, insurance, optional products, and any down payment or trade-in unless those amounts are already reflected in the amount financed.

What Goes Into a Car Payment?

The amount financed is not necessarily the car’s advertised price. It generally represents the amount borrowed after the transaction’s additions and deductions are accounted for. A down payment or trade-in credit can reduce the amount financed; taxes, fees, or optional items included in the loan can increase it. Enter the actual amount financed shown in the quote when you have it, rather than assuming it equals the vehicle price.

APR is the annual rate used for this estimate. The calculator treats it as a fixed annual rate divided into monthly periods; it does not determine or verify the APR on an offer. The loan term is the repayment duration, expressed here in years. A longer term usually produces a lower scheduled payment for the same principal and APR, but it also means more payment periods and can increase total interest.

How to Use and Interpret the Estimate

Enter the amount financed, APR as a percentage (for example, enter 8 for 8%), and term in years. The result is a scheduled monthly loan payment, not a complete estimate of the monthly cost of owning or operating a car. To compare the arithmetic of two scenarios, keep the assumptions clear and change one input at a time.

• Monthly payment: the recurring principal-and-interest amount under the formula’s assumptions.
• Total interest: the estimated interest paid over all scheduled payments, not the total amount paid including principal.
• Total of loan payments: monthly payment multiplied by the number of months. In the example, that is $405.53 × 60 = $24,331.80.

For a complete ownership budget, consider costs that are outside this loan calculation, such as insurance, fuel or charging, maintenance, parking, and taxes or fees. Those costs vary and are not inferred by the calculator. Get the relevant figures from the applicable provider or quote instead of treating them as part of the estimated payment.

Common Estimate Gaps and Limitations

A frequent mistake is entering the vehicle’s sticker price when the amount borrowed is different. Another is confusing an APR entered as a percent with a decimal: 8% belongs in the APR field as 8, not 0.08. The calculator’s term field is in years, while the formula converts that value to months. Rounding can also create a small difference from a lender’s final schedule, especially when payment dates or daily interest calculations are involved.

This is a level-payment estimate, not a quote or approval decision. It does not model a changing rate, irregular payment dates, a balloon payment, skipped or deferred payments, or extra payments. It also does not calculate a separate trade-in payoff or determine how taxes and fees are handled in a transaction. Use the lender’s disclosed amount financed, APR, term, and payment schedule for the actual offer details.

Frequently Asked Questions

How do I estimate a car payment?
Use the amount financed, annual percentage rate, and loan term in a fixed-payment loan formula. This calculator converts APR to a monthly rate and the term to a number of monthly payments.

Does the estimate include insurance or taxes?
No. It estimates principal and interest only. Insurance, taxes, fees, and other ownership costs are not included unless they have already been added to the amount financed.

Why does a longer car loan have a lower monthly payment?
The borrowed amount is spread across more scheduled payments. That can reduce each payment, while the longer repayment period may increase the total interest calculated over the loan.

Is APR the same as the monthly interest rate?
No. APR is entered as an annual percentage. This calculator divides it by 1,200 to estimate the monthly rate used in its formula.

Why might my lender’s payment differ?
The quoted amount financed, APR, term, payment dates, included charges, or rounding may differ from the inputs and assumptions here. Compare the calculator inputs with the lender’s disclosed figures.

This 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 | $ | p * (apr / 1200) / (1 - (1 + apr / 1200) ^ -(yrs * 12)) | 2
out int | Total interest | $ | pmt * yrs * 12 - p | 2