Shopping for a car is exciting, but the sticker price is only the beginning. Once you add tax, fees, interest, insurance, and a multi-year loan, the car you drive off the lot can end up costing tens of thousands of dollars more than the number on the window. This auto loan calculator takes the full picture — vehicle price, down payment, trade-in, sales tax, dealer fees, loan term, APR, and even your insurance and income — and shows you the real monthly number before you sign anything.
Slide the inputs and every figure updates instantly. You will see the amount financed, the principal-and-interest payment, the all-in monthly cost with insurance, the total interest over the life of the loan, the total cost of the car, and what fraction of your paycheck the car eats.
How to Use
- Enter the Vehicle Price — the negotiated out-the-door price you have agreed to pay, before tax and fees.
- Set your Down Payment in dollars. More cash down shrinks the amount financed and cuts total interest; 20% is a healthy target but not required.
- Add your Trade-In Value. If you owe more on your current car than it is worth, enter the negative equity as a negative number — it gets rolled into the new loan.
- Type your Sales Tax Rate (state plus local). Leave it at 0 only if you will pay the tax out of pocket; most dealers fold it into the loan.
- Enter the Doc & Registration Fee the dealer quoted. These vary by state and dealer and are usually financed as well.
- Pick the Loan Term in months — 60 is the default for new cars, but 72- and 84-month terms are common. A longer term lowers the payment but costs far more in interest.
- Type the Interest Rate (APR) the lender quoted. If you have not applied yet, use the national average for your credit tier and test ±1% to stress-test your budget.
- Add your Monthly Insurance estimate. This is not part of the bank loan, but it is part of what you actually pay to drive the car.
- Enter your Monthly Gross Income. The calculator shows your payment-to-income ratio and flags it as tight if the all-in car payment exceeds 10% of your take-home.
The result card breaks out the amount financed, the P&I payment, the all-in monthly cost (the highlighted number you should budget against), total interest, the total cost of the car, and your payment-to-income ratio.
The Auto Loan Formula
Your monthly principal-and-interest payment comes from the same amortization formula used by every major US lender and the CFPB:
M = P × r(1 + r)ⁿ / ((1 + r)ⁿ − 1)
Where:
- M is the monthly payment.
- P is the amount financed — (vehicle price − down payment − trade-in) grossed up by sales tax, plus doc fees.
- r is the monthly interest rate — the annual APR divided by 12.
- n is the total number of monthly payments — the loan term in months.
Worked example: a $30,000 car with $5,000 down, no trade-in, 7% sales tax, $500 doc fee, a 60-month term, and a 6.9% APR. The amount financed is roughly $27,550, the monthly rate is 0.00575, and n = 60. The P&I payment lands near $543 per month, and over five years the total interest is about $2,560. Adding $120 of insurance pushes the all-in cost near $663 per month.
If the APR is 0% (a manufacturer subvention deal), the formula divides by zero, so the engine simply splits the principal evenly across the number of months: a $25,000 loan over 60 interest-free months is $416.67 per month with zero interest.
Why the All-In Number Matters
Lenders approve you based on the loan payment, but you actually pay insurance, gas, maintenance, and registration on top. A $420 P&I payment can feel affordable on paper, but once $150 of insurance, $180 of gas, and $80 of maintenance are added, the car is consuming $830 a month — nearly a sixth of a $5,000 monthly gross paycheck. That is why this calculator folds in insurance and income, not just the bank's payment.
Aim to keep your all-in transportation cost under 10–15% of your gross monthly income. Above that, a single unexpected repair, medical bill, or furlough can put the loan — and the car — at risk.
Term Length: 60 vs 72 vs 84 Months
Longer terms have become normal, but they are a trap for buyers who focus only on the monthly payment:
- 48 months at 6.9% on a $25,000 loan: about $598/month, total interest around $3,700.
- 60 months at 6.9%: about $494/month, total interest around $4,600.
- 72 months at 6.9%: about $425/month, total interest around $5,600.
- 84 months at 6.9%: about $378/month, total interest around $6,800.
Stretching from 60 to 84 months cuts the payment by $116 but adds $2,200 of interest and leaves you "underwater" — owing more than the car is worth — for two extra years. Choose the shortest term you can actually afford, and use a manufacturer 0% APR deal as the free-money lever it is.
Examples
Example 1 — The default new-car buyer. You pick out a $30,000 sedan, put $5,000 down, trade in nothing, pay 7% sales tax and a $500 doc fee, finance for 60 months at 6.9%, and carry $120/month insurance on a $5,000 monthly paycheck. The amount financed is about $27,550, the P&I payment is near $543/month, and the all-in cost with insurance is roughly $663/month — about 13% of gross income. Over the life of the loan you will pay roughly $2,560 in interest on top of the $25,000 principal.
Example 2 — Beating the 0% APR offer. On the same $30,000 car with $5,000 down, the dealer advertises 0% APR for 60 months. The payment drops to about $458/month with zero interest — saving over $2,500 compared with the 6.9% offer. Always run the numbers both ways: sometimes the cash rebate beats 0% financing, and this calculator lets you swap the rate and see the difference.
Example 3 — Stress-testing a luxury purchase. On a $70,000 SUV with $10,000 down, 8% tax, a 72-month term at 7.5% APR, and $180 insurance, the P&I payment alone is near $1,100/month — and the all-in cost crosses $1,300/month. On a $6,000 monthly paycheck that is over 20% of gross, which is a warning sign. Running this math before you fall in love with a vehicle prevents a six-year commitment you can not actually afford.
FAQ
How is an auto loan monthly payment calculated?
The payment uses the standard amortization formula M = P × r(1+r)ⁿ / ((1+r)ⁿ − 1), where P is the amount financed (price minus down and trade-in, plus tax and fees), r is the monthly interest rate (APR divided by 12), and n is the number of monthly payments (loan term in months). This is the same formula used by Bankrate, NerdWallet, and the CFPB.
How much should I put down on a car?
Aim for 10–20% of the purchase price. 20% down protects you from going underwater early, helps you qualify for a better APR, and cuts total interest sharply. If you have to choose between a larger down payment and an emergency fund, keep the emergency fund and put down the minimum that gets you a decent rate.
Is it better to finance for 60 or 72 months?
Mathematically, the shorter 60-month loan is cheaper: a $25,000 loan at 6.9% costs about $4,600 in interest over 60 months versus $5,600 over 72. The 72-month payment is about $70 lower, but you pay an extra $1,000 and stay underwater longer. Choose 72 only if the lower payment is the difference between affording a safe car and not affording one, and pay extra when you can.
Does sales tax get rolled into the auto loan?
In most states, yes. Dealers calculate the tax on the negotiated price and add it to the amount financed unless you pay it in cash. This calculator lets you enter your sales tax rate; set it to 0 if you will pay the tax separately. Remember that financing the tax means you pay interest on the tax, which raises the effective cost of the car.
Can I pay off my car loan early?
Most auto loans in the US are simple-interest loans with no prepayment penalty, so extra payments go straight to principal and save you interest. Even an extra $50 a month on a $25,000, 60-month loan at 6.9% can cut several months off the term and save hundreds of dollars. Always confirm there is no prepayment penalty in your contract before planning to prepay.
What is a good APR on a car loan?
As of recent national averages, excellent credit (750+) qualifies for around 4–6% on new cars; good credit (700–749) lands around 6–8%; average credit (620–699) pays 8–12%; and sub-620 credit can exceed 12%. Manufacturer 0% or 1.9% APR deals are subvention offers reserved for buyers with top-tier credit. Check your credit score before you shop, and shop at at least three lenders — credit unions often beat dealer financing by a full percentage point or more.
Disclaimer
This auto loan calculator is provided for informational purposes only and does not constitute financial, lending, or tax advice. Estimates are based on the inputs you enter and the standard amortization formula; actual offers vary by lender, credit profile, state, and dealer. Insurance, tax, and fee figures are approximations. Always confirm your final payment and terms directly with a licensed lender or dealer before committing to an auto loan.