Auto Calculator

by
Auto Loan Calculator
Calculate Monthly Payment
Results:
Monthly Payment: $0.00
Total Principal:
$0.00
Total Interest:
$0.00
Total Loan Cost:
$0.00
function calculateResult(){var price=parseFloat(document.getElementById('autoPrice').value);var down=parseFloat(document.getElementById('downPayment').value)||0;var trade=parseFloat(document.getElementById('tradeValue').value)||0;var taxRate=parseFloat(document.getElementById('salesTax').value)||0;var interest=parseFloat(document.getElementById('interestRate').value);var term=parseFloat(document.getElementById('loanTerm').value);if(isNaN(price)||isNaN(interest)||isNaN(term)||price<=0||term<=0){alert('Please enter valid positive numbers for Price, Interest Rate, and Term.');return;}var taxAmount=price*(taxRate/100);var principal=price-down-trade+taxAmount;if(principal<=0){document.getElementById('monthlyPaymentDisplay').innerHTML='$0.00';document.getElementById('totalPrincipalDisplay').innerHTML='$0.00';document.getElementById('totalInterestDisplay').innerHTML='$0.00';document.getElementById('totalCostDisplay').innerHTML='$0.00';return;}var monthlyRate=(interest/100)/12;var payment=(principal*monthlyRate)/(1-Math.pow(1+monthlyRate,-term));if(interest===0){payment=principal/term;}var totalCost=payment*term;var totalInterest=totalCost-principal;document.getElementById('monthlyPaymentDisplay').innerHTML='$'+payment.toLocaleString(undefined,{minimumFractionDigits:2,maximumFractionDigits:2});document.getElementById('totalPrincipalDisplay').innerHTML='$'+principal.toLocaleString(undefined,{minimumFractionDigits:2,maximumFractionDigits:2});document.getElementById('totalInterestDisplay').innerHTML='$'+totalInterest.toLocaleString(undefined,{minimumFractionDigits:2,maximumFractionDigits:2});document.getElementById('totalCostDisplay').innerHTML='$'+totalCost.toLocaleString(undefined,{minimumFractionDigits:2,maximumFractionDigits:2});if(document.getElementById('showSteps').checked){var stepsText='Calculation Summary:
Loan Amount = Price ($'+price.toFixed(2)+') – Down ($'+down.toFixed(2)+') – Trade ($'+trade.toFixed(2)+') + Tax ($'+taxAmount.toFixed(2)+') = $'+principal.toFixed(2)+'
Monthly Rate = '+(interest/12).toFixed(4)+'%
Total Number of Payments = '+term;document.getElementById('stepsOutput').innerHTML=stepsText;document.getElementById('stepsOutput').style.display='block';}else{document.getElementById('stepsOutput').style.display='none';}}

Calculator Use

This auto calculator is designed to help you estimate your monthly car loan payments, total interest, and the overall cost of a vehicle purchase. Whether you are buying a new or used car, understanding your financing is crucial for staying within your budget.

By adjusting variables like your down payment, trade-in value, and sales tax, you can see exactly how much car you can afford before you ever step foot on a dealership lot.

Auto Price
The total purchase price of the vehicle before any taxes, fees, or down payments are applied.
Down Payment
The cash amount you pay upfront. A higher down payment reduces your loan principal and monthly payment.
Trade-in Value
The credit given to you by a dealer for your old vehicle. Like a down payment, this reduces the total amount you need to borrow.
Interest Rate (APR)
The Annual Percentage Rate charged by the lender for borrowing the money. Your credit score heavily influences this rate.
Loan Term
The length of the loan in months (e.g., 36, 48, 60, or 72 months).

How It Works

The auto calculator uses the standard amortization formula to determine your monthly payment. First, it calculates the "Principal" by subtracting your down payment and trade-in value from the vehicle price, then adding the applicable sales tax.

PMT = P [ r(1 + r)^n ] / [ (1 + r)^n – 1 ]

  • PMT = Monthly Payment
  • P = Principal Loan Amount (Price – Down – Trade + Tax)
  • r = Monthly Interest Rate (Annual Rate / 12)
  • n = Number of Months (Loan Term)

Calculation Example

Example: You are purchasing a car for $35,000 with a $5,000 down payment and a trade-in value of $2,000. Your local sales tax is 7%, your interest rate is 5%, and the term is 60 months.

Step-by-step solution:

  1. Calculate Tax: $35,000 * 0.07 = $2,450
  2. Calculate Principal (P): $35,000 – $5,000 – $2,000 + $2,450 = $30,450
  3. Monthly Interest Rate (r): 0.05 / 12 = 0.004167
  4. Calculate Payment (PMT): $30,450 * [0.004167(1.004167)^60] / [(1.004167)^60 – 1]
  5. Monthly Result: $574.63
  6. Total Interest: ($574.63 * 60) – $30,450 = $4,027.80

Common Questions

How does a trade-in affect my car loan?

A trade-in acts exactly like a down payment. It reduces the amount you need to finance. In many states, you only pay sales tax on the "net price" (Auto Price minus Trade-in), which can save you even more money. Our auto calculator adds tax to the full price by default, but you can adjust your inputs to reflect local laws.

Is a longer loan term better?

A longer term (like 72 or 84 months) results in a lower monthly payment, making the car more affordable month-to-month. However, you will pay significantly more in total interest over the life of the loan. Use the auto calculator to compare a 48-month term vs. a 72-month term to see the interest difference.

What is a good interest rate for a car?

Interest rates vary based on your credit score, the lender, and whether the car is new or used. Typically, new cars have lower rates (sometimes as low as 0-3%), while used cars range from 5% to 15% or higher for subprime borrowers.

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