Math Practice Activity 7 Calculating Interest Rates

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Auto Lease Payment Calculator

24 Months 36 Months 48 Months 60 Months
Note: APR / 2400 = Money Factor

Estimated Monthly Payment

$0.00
Monthly Depreciation:
$0.00
Monthly Rent Charge:
$0.00
Monthly Tax:
$0.00
Total Lease Cost:
$0.00
function calculateLease() { var msrp = parseFloat(document.getElementById('msrp').value) || 0; var negotiatedPrice = parseFloat(document.getElementById('negotiatedPrice').value) || 0; var downPayment = parseFloat(document.getElementById('downPayment').value) || 0; var tradeIn = parseFloat(document.getElementById('tradeIn').value) || 0; var term = parseFloat(document.getElementById('leaseTerm').value) || 1; var residualPercent = parseFloat(document.getElementById('residualPercent').value) || 0; var moneyFactor = parseFloat(document.getElementById('moneyFactor').value) || 0; var salesTax = parseFloat(document.getElementById('salesTax').value) || 0; // 1. Calculate Residual Value var residualValue = msrp * (residualPercent / 100); // 2. Adjusted Capitalized Cost var adjCapCost = negotiatedPrice – downPayment – tradeIn; // 3. Monthly Depreciation var monthlyDepreciation = (adjCapCost – residualValue) / term; if (monthlyDepreciation < 0) monthlyDepreciation = 0; // 4. Monthly Rent Charge (Interest) var monthlyRentCharge = (adjCapCost + residualValue) * moneyFactor; // 5. Pre-tax Payment var basePayment = monthlyDepreciation + monthlyRentCharge; // 6. Tax var monthlyTax = basePayment * (salesTax / 100); // 7. Total Monthly Payment var totalMonthlyPayment = basePayment + monthlyTax; // 8. Total Cost over Lease var totalCost = (totalMonthlyPayment * term) + downPayment + tradeIn; // Display Results document.getElementById('results-area').style.display = 'block'; document.getElementById('monthlyPaymentDisplay').innerText = '$' + totalMonthlyPayment.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}); document.getElementById('depreciationPart').innerText = '$' + monthlyDepreciation.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}); document.getElementById('rentPart').innerText = '$' + monthlyRentCharge.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}); document.getElementById('taxPart').innerText = '$' + monthlyTax.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}); document.getElementById('totalLeaseCost').innerText = '$' + totalCost.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}); }

How Car Lease Payments are Calculated

Understanding car lease math is the best way to ensure you are getting a fair deal at the dealership. Unlike a traditional auto loan, where you pay for the entire value of the car, a lease only charges you for the portion of the car's value you use during the term.

The Three Main Components of a Lease

  1. Depreciation Fee: This is the value the car loses during your lease. It is calculated by taking the Adjusted Capitalized Cost (the price you pay) and subtracting the Residual Value (what the car is worth at the end).
  2. Rent Charge: This is essentially the interest. Dealers use a "Money Factor" instead of an APR. To convert a Money Factor to a traditional interest rate, multiply it by 2400.
  3. Taxes and Fees: Most states charge sales tax on the monthly payment, though some states require the tax to be paid upfront.

What is Residual Value?

The residual value is a prediction of what the vehicle will be worth at the end of the lease. It is set by the bank, not the dealer. A higher residual value is actually better for you because it means the car depreciates less, resulting in a lower monthly payment.

Example Calculation

Imagine you are leasing a car with a $40,000 MSRP and you negotiate the price down to $38,000. If the residual value is 60% after 36 months, the car will be worth $24,000 at the end. Your depreciation cost is $38,000 – $24,000 = $14,000. Divided by 36 months, your base depreciation payment is $388.88 per month (plus interest and tax).

Pro Tips for Lowering Your Payment

  • Negotiate the Sale Price: Even though it's a lease, you can still negotiate the capitalized cost just like a purchase.
  • Check the Money Factor: Ask the dealer for the "buy rate" money factor to ensure they aren't marking up the interest rate.
  • Watch the Mileage: Increasing your annual mileage limit (e.g., from 10k to 12k miles) lowers the residual value, which increases your monthly payment.

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