Car Loan Calculator With Down Payment

A car loan calculator with a down payment estimates your monthly payment and total interest after subtracting your down payment from the vehicle’s price. Enter the amount financed, APR, and loan term to see the estimate; use the down-payment conversion below to calculate the amount financed from a vehicle price.

Formula

The calculator uses the standard fixed-payment loan formula. The amount financed is the vehicle’s agreed price and eligible costs minus the down payment and any trade-in credit applied to the purchase. Calculate that amount separately, then enter it as p.

• Monthly payment: M = P × r ÷ [1 − (1 + r)⁻ⁿ], rounded to the nearest cent.
• Total interest: I = (M × n) − P. The calculator uses the rounded monthly payment for this total.

Here, P is the amount financed in dollars, r is the monthly interest rate as a decimal (APR ÷ 1,200), n is the number of monthly payments (years × 12), M is the monthly principal-and-interest payment in dollars, and I is total interest in dollars over the stated term. APR is entered as a percentage per year.

Worked Example

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

1. Convert APR to a monthly decimal rate: 8 ÷ 1,200 = 0.0066667.
2. Convert the term to payments: 5 × 12 = 60 months.
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.

How to Include a Down Payment

The calculator takes the amount borrowed, not the vehicle’s sticker price or the cash paid at signing. Work out the amount financed before entering it. For a simple purchase with no trade-in or other costs, subtract the down payment from the negotiated vehicle price.

For example, a $25,000 vehicle price less a $5,000 down payment gives $20,000 to finance. At the default APR and term, the calculator estimates a $405.53 monthly payment and $4,331.80 in interest. This example isolates the arithmetic; actual contracts can include other amounts.

A more complete estimate is: vehicle price + eligible taxes and fees + optional products added to the loan − down payment − trade-in credit applied = amount financed. Whether a particular charge can be financed depends on the transaction. Use the amount shown in the lender’s written breakdown when available, and avoid counting a down payment twice.

When to Use the Estimate

Use the result to understand how the amount borrowed, APR, and term affect the scheduled principal-and-interest payment. You can run separate calculations with different inputs to examine the arithmetic. Keep the purchase price, down payment, APR, and term consistent with the figures you are comparing; a lower payment by itself does not show the full cost because a longer term can mean more payments and more interest.

The displayed monthly payment is not necessarily the full monthly cost of owning or operating a vehicle. It excludes recurring expenses such as insurance, fuel, maintenance, and registration, as well as any taxes or charges not included in the loan amount. The total-interest output also does not include those excluded costs.

Common Input Problems and Limits

• Entering the price instead of the loan amount: If you enter the full vehicle price without subtracting the down payment, the estimate treats the down payment as if it were not made.
• Mixing APR and monthly rates: Enter APR as an annual percentage, such as 8—not 0.08 or a monthly rate. The formula converts it to a monthly rate.
• Using years as months: Enter a term in years. The calculator multiplies it by 12 to find the payment count.
• Rounding early: The payment is rounded to cents, and total interest uses that rounded payment. A lender’s final schedule can differ slightly because of payment dates, daily interest calculations, or contract-specific rounding.
• Leaving out financed costs: If a charge is added to the loan, include it in the amount financed; if it is paid separately, do not add it to that amount.

This is a standard estimate for a fixed APR and equal monthly payments. It assumes the loan is fully repaid through those payments, with no skipped payments, extra payments, changing rate, or separate final payment. The formula does not model a lease, a balloon payment, late charges, or lender-specific payment schedules.

Assumptions

• The APR stays fixed for the full term.
• Payments are equal monthly payments made at the end of each monthly period.
• Interest compounds monthly using APR ÷ 12.
• Fees, taxes, insurance, optional products, and other charges are excluded unless included in the entered loan amount; the calculator has no separate inputs for them.

Frequently Asked Questions

Does a down payment lower the monthly car payment?
It lowers the payment when it reduces the amount financed, while the APR and term stay the same. The size of the change depends on the loan inputs.

Should I enter the down payment as a negative number?
No. This calculator asks for the amount financed after subtracting the down payment. Enter a positive loan amount; do not subtract the down payment again in the calculator.

Does the estimate include taxes and fees?
No separate tax or fee fields are provided. Add any charges that will be financed to the loan amount, and leave out charges paid separately.

Why might my lender’s payment differ?
The contract may use a different financed amount, payment date, interest calculation method, rounding convention, or payment schedule. Compare the inputs and the lender’s disclosure to identify the difference.

Does total interest include my down payment?
No. The down payment is not borrowed, so it is not part of loan interest. The output is interest on the entered amount financed over the calculated term.

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

Related

• Bad Credit Car Loan With No Down Payment?
• Auto Loan Down Payment Calculator and Guide
• Auto Loan Payoff Calculator: Estimate Your Balance

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