Auto Loan Calculator — Monthly Payment & Amortization

How the Auto Loan Calculator Works

We compute the financed amount from your inputs, then apply the standard amortization formula for monthly payments. Everything runs client-side for privacy.

Financed Amount

taxable = price − (taxAfterTrade ? tradeIn : 0)
tax = max(0, taxable) × (taxRate/100)
financed = price + fees + tax − down − tradeIn

Monthly Payment

With monthly rate r = APR/12/100 and term n months:
payment = financed × [ r / (1 − (1 + r)−n) ]
When you enter an extra monthly payment, we simulate early payoff month-by-month.

Privacy

No data leaves your browser. There are no uploads or server calls.

Frequently Asked Questions

How is sales tax applied?

Many regions tax the price minus trade-in; others tax the full price. Use the toggle to match your area.

What compounding does APR use here?

We assume nominal APR with monthly compounding and equal monthly payments, which matches most auto loans.

Can I see the amortization schedule?

Yes. After you calculate, expand the amortization section to see month-by-month principal, interest, and balance.

Is my data private?

Yes—everything runs locally in your browser.

Understanding Auto Loans: A Practical Guide

Auto loans finance a vehicle purchase by spreading the cost over time. Your monthly payment is driven by five levers: price, down payment, trade-in, APR, and term length. Taxes and fees affect the amount you actually finance. This section explains each piece and how to optimize your costs.

APR vs. Interest Rate

The interest rate is the cost of borrowing money. APR (Annual Percentage Rate) folds in the rate plus certain lender costs. Two loans with the same nominal rate can have different APRs if one includes extra charges. Our calculator uses APR with monthly compounding to match how most auto loans are quoted.

How Taxes and Fees Affect the Financed Amount

You don’t pay interest on the sticker price alone. You typically finance: price + tax + fees − down − trade-in. Whether sales tax applies before or after trade-in depends on your locale—use the toggle to match your rules.

Monthly Payment Formula, Simply Explained

With monthly rate r = APR/12 and n months, the payment is: payment = financed × [ r / (1 − (1 + r)−n) ]. Lowering APR, increasing down payment, or shortening the term reduces interest paid over the life of the loan.

Early Payoff & Extra Payments

Extra principal payments reduce your balance sooner, shrinking future interest charges. Our calculator simulates this month-by-month. Check your lender’s policy for any prepayment penalties (many auto loans allow prepayment without fees).

Common Pitfalls to Avoid

• Focusing only on the monthly payment: A very long term can look affordable but increases total interest.
• Rolling fees into the loan: Convenience adds interest on top of fees. Paying fees upfront reduces total cost.
• Negative equity trade-ins: Owing more than your current car’s value can inflate the new loan.
• Skipping taxes/fees assumptions: Make sure the tax toggle matches your region to avoid under/overestimates.

Quick Optimization Checklist

• Compare APR offers from banks, credit unions, and dealers.
• Increase your down payment to shrink the financed amount.
• Pick the shortest term you can comfortably afford.
• Add a small monthly extra (e.g., $25–$50) to accelerate payoff.