Auto Loan Calculator — Monthly Payments & Total Cost
Calculate your car loan monthly payment, total interest, and total cost of ownership. Enter the vehicle price, down payment, trade-in value, interest rate, and loan term (12–84 months). See a breakdown of sales tax and fees, compare different loan terms side by side, and check if your payment fits within the recommended 15–20% of monthly income budget. Whether you are buying a new or used car, this calculator helps you understand the true cost of your auto loan before you visit the dealership.
Understanding Your Result
How Auto Loan Payments Are Calculated
Your monthly payment is calculated using the standard amortization formula: M = P[r(1+r)^n] / [(1+r)^n - 1], where P is the loan amount (vehicle price minus down payment and trade-in, plus sales tax and fees), r is the monthly interest rate, and n is the number of payments. This formula ensures that each payment covers the interest accrued that month while gradually reducing the principal balance.
What Is the Loan Amount?
The loan amount is not just the vehicle price. It is calculated as: Vehicle Price − Down Payment − Trade-In Value + Sales Tax + Title/License Fees. For example, a $35,000 new car with a $5,000 down payment, $3,000 trade-in, 6.5% sales tax ($1,950), and $200 in fees results in a loan amount of $33,750. Many borrowers focus only on the sticker price and forget to include taxes and fees, which can add thousands to their loan.
Why Does Loan Term Matter?
The loan term is one of the biggest factors affecting both your monthly payment and total cost. A shorter term means higher monthly payments but significantly less total interest. A longer term lowers your payment but costs more over the life of the loan. For example, a $30,000 loan at 7% over 36 months costs $2,183 in interest, while over 72 months it costs $4,440 — more than double. Financial experts recommend keeping your auto loan term at 60 months or fewer whenever possible.
The 20/4/10 Rule
A widely cited guideline for responsible auto buying is the 20/4/10 rule: put at least 20% down, finance for no more than 4 years, and keep your total transportation costs below 10% of your gross monthly income. This rule helps prevent overextending yourself on a vehicle purchase.
New vs. Used Car Loans
New cars typically qualify for lower interest rates and manufacturer subventions (sometimes as low as 0.9% APR), but they depreciate fastest in the first few years — losing about 20% of their value the moment you drive off the lot. Used cars have higher rates but depreciate more slowly, meaning you are less likely to go upside down (owing more than the car is worth). If you plan to keep the car for a long time, a reliable used car often makes more financial sense.
Affordability Check
The affordability check uses the recommended guideline that car payments should not exceed 15–20% of your gross monthly income. If your payment exceeds 20%, consider increasing your down payment, extending the term, or choosing a less expensive vehicle. Note that this check only considers the loan payment — it does not include insurance, fuel, maintenance, or registration costs, which can add another $200–$400 per month.
Frequently Asked Questions
Your monthly payment uses the standard amortization formula: M = P[r(1+r)^n] / [(1+r)^n - 1], where P is the loan amount (vehicle price minus down payment and trade-in, plus sales tax and fees), r is the monthly interest rate, and n is the number of payments. For example, a $30,000 loan at 7% over 60 months results in a monthly payment of approximately $594.
The loan amount is not just the vehicle price. It includes: Vehicle Price − Down Payment − Trade-In Value + Sales Tax + Title/License Fees. For example, a $35,000 new car with a $5,000 down payment, $3,000 trade-in, 6.5% sales tax ($1,950), and $200 in fees results in a loan amount of $33,750. Many borrowers focus only on the sticker price and forget to include taxes and fees, which can add thousands to their loan.
Auto loan rates depend heavily on your credit score. Borrowers with excellent credit (720+) typically qualify for rates between 4% and 6%. Those with fair credit (640–719) often see rates of 6% to 10%. Borrowers with poor credit (below 640) may face rates from 10% to 20% or more. New cars usually have lower rates than used cars, and manufacturer subventions can offer rates as low as 0.9% or even 0% on select models.
Auto loan terms range from 24 to 84 months. While longer terms mean lower monthly payments, they also mean significantly more total interest. Financial experts recommend keeping your auto loan term at 60 months or fewer whenever possible. For example, a $30,000 loan at 7% over 36 months costs $2,183 in interest, while over 72 months it costs $4,440 — more than double.
The 20/4/10 rule is a widely cited guideline for responsible auto buying: put at least 20% down, finance for no more than 4 years, and keep your total transportation costs (payment + insurance + fuel) below 10% of your gross monthly income. This rule helps prevent overextending yourself on a vehicle purchase and ensures you are not spending too much of your budget on a depreciating asset.
New cars come with lower interest rates and manufacturer incentives, but they depreciate fastest in the first few years — losing about 20% of their value the moment you drive off the lot. Used cars have higher rates but depreciate more slowly, meaning you are less likely to go upside down (owing more than the car is worth). If you plan to keep the car for a long time, a reliable used car often makes more financial sense.
A trade-in reduces the amount you need to borrow, lowering both your monthly payment and total interest. The trade-in value counts toward your down payment. However, make sure you get a fair offer — dealerships often undervalue trade-ins. You can get an independent appraisal from sources like Kelley Blue Book or CarMax before visiting the dealership to negotiate from a stronger position.
Zero-percent financing sounds too good to be true — and sometimes it is. Manufacturers typically offer 0% APR on well-equipped models that are sitting on lots, or on new vehicles where they want to boost sales. The catch is that 0% financing often comes with stricter credit requirements and may mean giving up other incentives like cash rebates. Compare the 0% offer against the rebate option — sometimes financing at 3–4% APR and taking a $3,000 rebate saves you more money overall.
Financial experts recommend that your car payment (plus insurance and fuel) should not exceed 10–15% of your gross monthly income. Some guidelines suggest keeping the payment itself under 20% of your monthly income. This calculator includes an optional affordability check that shows your payment as a percentage of income and color-codes it: green for healthy (≤15%), yellow for caution (15–20%), and red for risky (>20%).
Being upside down (or "underwater") means you owe more on your car loan than the vehicle is currently worth. This commonly happens when you make a small down payment, choose a long loan term, or drive a car that depreciates quickly. If you need to sell or trade in an upside-down car, you would need to pay the difference out of pocket. To avoid this, aim to put down at least 20%, keep your loan term to 60 months or fewer, and consider gap insurance if you finance more than 100% of the car's value.
When you shop for auto loans, lenders perform a soft credit check to give you a rate quote, which does not affect your credit score. Only a hard credit inquiry (when you actually apply for a loan) will temporarily lower your score by a few points. However, multiple hard inquiries within a short window (typically 14–45 days) are usually treated as a single inquiry by credit scoring models, so rate shopping within a focused period has minimal impact.
Sales tax rates vary widely by state and locality. Some states have no sales tax on cars (Delaware, Montana, Oregon, New Hampshire), while others charge over 7%. Many states also add local county or city taxes on top of the state rate. Check your state's department of revenue website or consult with the dealer before shopping to understand your total tax burden. Note that some states allow you to deduct the trade-in value from the taxable amount, while others do not.