New Car Payment Calculator With Trade-In

This new car payment calculator with trade-in estimates your monthly payment after subtracting the trade-in value and accounting for any loan balance on your current car. Enter the amount financed, annual APR, and loan term to see the estimated payment and total interest; use the formula below to work out the amount financed from the vehicle price and trade-in figures.

Formula

The calculator uses the standard fixed-payment loan formula. First, estimate the amount financed by combining the purchase price and other amounts included in the deal, then subtracting the trade-in equity and any cash down payment:

Amount financed = vehicle price + amount added to financing − trade-in equity − cash down payment

Trade-in equity = trade-in allowance − current loan payoff

For the calculator’s payment, let P be the loan amount in dollars, a the APR in percent per year, and y the term in years. The number of monthly payments is n = 12y, and the monthly rate as a decimal is r = a / 1200.

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

Total interest = monthly payment × n − P

The block’s first output is the monthly payment, rounded to cents. Its second output estimates total interest using that rounded payment. This is a loan-payment calculator: it does not determine a vehicle’s market value, calculate a trade-in offer, or establish the final amount financed from a vehicle price automatically.

Worked Example

Using exactly the calculator defaults—$20,000 loan amount, 8% APR, and a five-year term:

• Monthly rate: 8 ÷ 1,200 = 0.0066667.
• Number of payments: 5 × 12 = 60.
• Monthly payment: $20,000 × 0.0066667 ÷ [1 − (1.0066667)⁻⁶⁰] = $405.53, rounded to cents.
• Total interest: $405.53 × 60 − $20,000 = $4,331.80.

These figures are estimates under the stated formula. Small differences can occur if a lender calculates interest or rounds payments differently.

Assumptions

• The APR stays fixed throughout the term.
• Payments are equal monthly payments, with the first payment one month after the loan begins.
• Interest is calculated monthly at APR divided by 12.
• The estimate excludes fees, taxes, insurance, PMI, escrow, and other charges unless they are already included in the loan amount you enter.

How to Include a Trade-In

A trade-in affects the payment through its equity, not simply through the vehicle’s quoted value. If a dealer allows $8,000 for the old car and the payoff required to clear its loan is $5,000, the trade-in equity is $3,000. That amount reduces the new loan, assuming it is applied to the purchase.

If the payoff is higher than the allowance, the trade-in has negative equity. For example, an $8,000 payoff against a $6,000 allowance leaves $2,000 to account for. If that amount is added to the new financing, it increases the amount financed rather than reducing it. Confirm how the payoff and allowance are treated in the written deal figures; do not enter the allowance as if it were all available equity.

To estimate the calculator’s loan amount, gather the figures that apply to your transaction:

1. Start with the vehicle’s agreed purchase price.
2. Add any taxes, fees, optional products, or negative equity that will actually be financed. The calculator does not look these up.
3. Subtract the trade-in allowance, then add back the old loan payoff. This is equivalent to subtracting trade-in equity.
4. Subtract any cash down payment applied to the purchase.
5. Enter the resulting estimated amount financed, along with the APR and term shown in the lender’s offer or disclosure.

Reading the Results and Comparing Scenarios

The monthly payment is the scheduled amount under a level-payment loan, not the vehicle’s full ownership cost. Fuel, maintenance, registration, insurance, and other ongoing expenses are outside this calculation. Total interest is the estimated interest across all scheduled payments; it is not the total amount paid for the car, because the principal is separate.

To see how assumptions affect the arithmetic, calculate separate scenarios by changing one input at a time. A larger amount financed generally raises the payment. A longer term spreads repayment over more months and can lower the monthly payment, while the total interest may increase because interest accrues for longer. A different APR also changes the payment and interest. These are mathematical effects, not a determination of which transaction fits a person’s circumstances.

For an apples-to-apples comparison, use the same amount financed and term when examining APR differences, and the same APR and amount when examining term differences. Use the exact figures supplied for each proposed transaction, and remember that a trade-in allowance may differ between offers. The amount financed is the key number to check: a low quoted payment alone does not show the price, term, or total financing cost.

Common Mistakes and Calculator Limits

• Using trade-in value instead of equity: subtract the payoff from the allowance before treating the result as a down payment.
• Leaving out financed costs: taxes, fees, and optional products can change the principal if included in the loan. Add only amounts that apply and are actually financed.
• Mixing APR and monthly rates: enter annual APR as a percentage, such as 8 for 8%. The formula converts it to a monthly decimal.
• Comparing payments without terms: a payment quote depends on both the loan amount and the number of payments. Check those inputs as well as APR.
• Expecting an exact payoff schedule: this estimate assumes a fixed rate, equal payments, and monthly timing. Actual payment dates, rounding, charges, or contract terms can affect the lender’s figures.

The calculator requires a positive APR and a term stated in years. If a proposal uses a different payment frequency, variable interest, a balloon amount, or a fee structure that changes the effective borrowing cost, this formula may not reproduce its schedule. For the actual APR, payoff, amount financed, and payment dates, use the figures in the lender’s documents rather than estimating them from a vehicle listing.

Frequently Asked Questions

Does a trade-in always lower a new car payment?
Not necessarily. Positive trade-in equity can reduce the amount financed if applied to the purchase. If the payoff exceeds the trade-in allowance, the difference may add to the new financing instead.

How do I calculate my trade-in equity?
Subtract the current loan payoff from the trade-in allowance. For example, an $8,000 allowance and a $5,000 payoff leave $3,000 in estimated equity before considering how the deal applies it.

Should I enter the car price or amount financed?
Enter the estimated amount financed: the purchase price plus amounts included in financing, adjusted for trade-in equity and cash down payment. The vehicle price alone may not equal the loan principal.

Does the calculator include sales tax and fees?
No. It does not calculate taxes or fees. If any are included in the loan, include their amounts in the loan amount you enter; otherwise, they are not reflected in the result.

Why is my lender’s payment different?
The lender’s amount may reflect a different principal, APR, term, payment date, rounding method, or additional charges. Compare the calculator inputs with the lender’s disclosed figures and payment schedule.

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

Related

• Car Payment Schedule Calculator and Loan Basics
• Car Payment Schedule Calculator: Monthly Cost and Interest
• Car Payment Receipt: What It Shows and How to Get One

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