Car Payment Calculator: Estimate Your Monthly Cost

A car payment calculator estimates the monthly principal-and-interest payment on a fixed-rate auto loan. Enter the amount financed, annual percentage rate (APR), and loan term to see the estimated monthly payment and total interest.

Formula

The calculator uses the standard fixed-payment loan formula. It converts the annual APR to a monthly rate, then spreads repayment of the loan principal and interest across the scheduled number of monthly payments:

Payment = P × r ÷ [1 − (1 + r)⁻ⁿ]

• P is the amount financed, in dollars.
• r is the monthly interest rate as a decimal: APR ÷ 1,200. For an 8% APR, r = 0.08 ÷ 12.
• n is the number of monthly payments: loan term in years × 12.

The displayed payment is rounded to the nearest cent. Estimated total interest is the rounded monthly payment multiplied by the number of payments, minus the original loan amount. Because the payment is rounded, the last real payment can differ slightly from the others.

Worked Example

Using the calculator’s default values—$20,000 financed, 8% APR, and five years—the calculation is:

1. Monthly rate: 0.08 ÷ 12 = 0.0066667.
2. Number of payments: 5 × 12 = 60.
3. Payment before cent rounding: 20,000 × 0.0066667 ÷ [1 − (1.0066667)⁻⁶⁰] ≈ $405.53.
4. Total of scheduled payments using the rounded payment: $405.53 × 60 = $24,331.80.
5. Estimated total interest: $24,331.80 − $20,000 = $4,331.80.

So, under these assumptions, the estimated monthly payment is $405.53, and estimated total interest is $4,331.80.

Assumptions

• The APR is fixed for the full loan term.
• Payments are made monthly, at the end of each monthly period.
• Interest accrues monthly using APR ÷ 12.
• The calculation excludes fees, taxes, insurance, optional products, and any other amounts not entered as part of the loan principal.

What a Car Payment Includes

A lender’s scheduled auto-loan payment generally repays borrowed principal and interest. The calculator models those two elements only. It does not calculate the full cost of owning or operating a vehicle, and a quoted monthly amount may not include expenses paid separately.

For example, the amount financed may be more than the vehicle’s negotiated price if taxes, registration charges, dealer-installed items, or optional products are added to the loan. A down payment or trade-in credit can reduce the amount financed. To estimate the loan payment, use the amount that would actually be borrowed—not automatically the vehicle’s advertised price.

Insurance, fuel, maintenance, repairs, and recurring vehicle charges affect a household’s overall transportation spending, but they are not part of the principal-and-interest formula. Keep them separate when comparing the payment estimate with a complete ownership budget.

How to Choose the Inputs

• Loan amount: Enter the principal expected to be financed after accounting for any down payment, trade-in credit, or amounts added to the loan. If those details are not settled, calculate more than one plausible amount.
• APR: Use the APR supplied for the specific loan offer. APR is expressed annually; the formula converts it to a monthly rate. Do not enter a monthly rate in the APR field.
• Term: Enter the repayment period in years. A five-year term means 60 monthly payments; a six-year term means 72.

The calculator accepts an APR from 0.01% to 100% because the payment formula divides by the rate. For an actual estimate, use the rate and loan amount provided by the lender rather than treating the defaults as a quote or prediction. Loan terms and other offer details are also specific to the particular transaction.

Comparing Payments and Understanding Limits

Changing one input at a time helps explain how the estimate responds. With the same principal and APR, extending the term usually reduces the scheduled monthly payment, while increasing the number of months over which interest accrues. A shorter term generally concentrates repayment into fewer, larger payments. The calculator itself does not decide which structure is appropriate for a reader.

For a comparison to be meaningful, hold the other assumptions constant. Comparing two monthly payments without checking the loan amount, APR, term, and fees can conceal important differences. A lower payment alone does not establish that two offers have the same total repayment cost.

This is a mathematical estimate, not a lender’s payoff schedule. Actual figures can differ because of payment dates, rounding conventions, fees financed into the balance, or contract terms. A variable rate, irregular payment schedule, balloon payment, or extra principal payment is not represented by this fixed-rate, equal-monthly-payment formula. The lender’s disclosure and payment schedule provide the exact figures for an offer.

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 performs that calculation and rounds the payment to cents.

Does a car payment include insurance and taxes?
This estimate includes only principal and interest. Insurance and other costs are not included unless they are financed as part of the loan amount; ongoing expenses paid separately require their own estimates.

Why does a longer car loan have a lower monthly payment?
With the same principal and APR, a longer term divides repayment across more monthly payments. Interest accrues over more periods, so the monthly figure can fall even while total interest rises.

Is APR the same as the monthly interest rate?
No. APR is entered as an annual percentage. This calculator uses APR divided by 12 to form the monthly rate, so enter 8 for an 8% APR—not 0.08 as a monthly rate.

Why is my lender’s payment different from this result?
The loan amount, APR, payment timing, fees, rounding, or contract structure may differ from the calculator’s assumptions. Check the lender’s disclosure for the figures and terms used in the actual offer.

This result is an estimate for educational purposes, 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