When you take out a car loan, the interest is the amount you pay your lender for the opportunity to borrow it. Car payments are amortized over the life of your loan, which means that in addition to the amount you’ll pay each month to pay down your principal, you’ll also owe interest.
The interest rate you’ll be offered on your loan will vary depending on a number of factors, including your credit score and the length of your loan. Interest payments are a costly part of financing your car, so it’s important to understand how they’re calculated so you can get a clear sense of what a good interest rate is as you shop for an auto loan.
Key Points
• The formula for calculating interest on a car loan is: (Interest Rate / Number of Payments per Year) x Loan Balance = Interest Amount Owed
• Many auto loans use daily simple interest, where interest accrues daily based on the outstanding balance.
• As you make payments, your loan balance decreases, leading to a reduction in the interest portion of each subsequent payment. This means more of your payment goes toward the principal over time.
• Some lenders, especially those catering to subprime borrowers, may offer precomputed interest loans. In these loans, interest is calculated upfront and added to the principal.
• The length of your loan term and your interest rate significantly affect the total interest paid over the life of the loan. Shorter terms and lower rates generally lead to less interest paid.
How to Calculate Interest on a Car Loan
If you want to figure out how much interest you’ll be paying each month as you make payments on your auto loan, the easiest thing to do is to find an amortization calculator online and plug in the numbers.
To figure it out yourself, you’ll need the same basic information:
• Your interest rate
• How often you make payments
• Loan principal
Here is the formula to figure out how much of your monthly loan repayment goes to interest:
(Interest Rate / Number of Payments per Year) x Loan Balance = Interest Amount Owed
Let’s say you take out a five-year auto loan of $20,000 at an interest rate of 8 percent. If you’re making monthly payments, we’ll make the number of payments 12. Since we’re looking at your very first payment, the balance is still $20,000. Then, we plug in the other numbers:
(0.08 / 12) x $20,000 = $133.33. This is the amount of your first payment that will go toward interest
As you pay down the amount of your principal, the amount of each payment that’s going toward your interest will also grow smaller.
Car Loan Interest Formula
A car loan may include daily simple interest charges and a fixed monthly payment. This means a variable portion of your monthly payment may go toward principal and interest.
A larger portion of your monthly payment may go toward interest at the beginning of the term, and a smaller portion of your monthly payment may go toward interest near the end of the loan term.
As mentioned earlier, you can use this simple interest formula to calculate how much of your monthly payment goes toward interest:
(Interest Rate / Number of Payments per Year) x Loan Balance = Interest Amount Owed
The interest rate in this formula is expressed as a decimal. For example, a 5% interest rate would be expressed as 0.05.
Your outstanding loan balance decreases with each payment, so this formula could be applied each month to determine how much of your payment went toward interest charges in that particular month. This is the formula used by online amortization calculators to estimate total interest costs over the life of your car loan.
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Car Loan Interest Example Calculations
Here are some car loan interest example calculations:
48 Months at 3%
A 48-month car loan with a $25,000 loan balance, 3% annual percentage rate of interest, and $553.36 monthly payment would include the following interest charge:
(0.03 / 12) x $25,000 = $62.50 interest charge for the month in question
72 Months at 3%
A 72-month car loan with a $530.45 loan balance, 3% APR, and $531.78 monthly payment would include the following interest charge:
(0.03 / 12) x $530.45 = $1.33 interest charge for the month in question
48 Months at 6%
A 48-month car loan with a $25,000 loan balance, 6% APR, and $587.13 monthly payment would include the following interest charge:
(0.06 / 12) x $25,000 = $125 interest charge for the month in question
72 Months at 6%
A 72-month car loan with a $577.17 loan balance, 6% APR, and $580.05 monthly payment would carry the following interest charge:
(0.06 / 12) x $577.17 = $2.89 interest charge for the month in question
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Simple vs. Precomputed Interest
Most car loans use a simple interest formula, which is what we discussed in the last section. This means that the amount of interest you owe each month is a percentage based on your principal, or loan balance, as of the day your payment is due.
In some cases, especially for subprime borrowers, a car loan might use precomputed interest instead of simple interest. This means lenders calculate the amount of interest upfront and add it to the principal, then divide that total by the number of months in your loan term to get your monthly payment. Your payments don’t apply to interest and principal separately.
And if you make extra payments, you likely won’t be able to lower the amount of interest you pay over the life of the loan as much as you would by prepaying on a loan with simple interest. However, if you’re only going to make the minimum payment each month, it may not make much difference to you.
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How Is Interest Paid on a Car Loan?
The average interest rate on new car loans in the first quarter of 2025 stood at 7.1%, according to Edmunds.
In the early months of your loan, you’ll owe more interest, and a greater portion of your monthly payments will go toward paying it off. As your loan balance gets smaller, you’ll owe less interest. Thus interest will become a smaller portion of your monthly payment, and more of your money will go toward paying off your principal.
If you prepay your loan (meaning you make one or more larger payments than the amount due), you can pay down your principal faster, potentially decreasing the amount of interest you owe. Be aware that some lenders charge prepayment penalties, so check your loan agreement before making prepayments.
Is Car Loan Interest Tax Deductible?
Car loan interest is tax-deductible in limited cases. Traditional employees generally can’t deduct interest paid on a car loan, but self-employed taxpayers may deduct car loan interest if they use the car for business purposes.
A tax deduction can reduce the amount of income tax you may have to pay or increase the size of your tax refund. The car interest deduction is limited to self-employed taxpayers who pay interest on a car loan and use the vehicle for business purposes.
The amount of car loan interest a self-employed taxpayer may deduct is determined by how much the taxpayer uses the vehicle for business purposes. Self-employed taxpayers who use their vehicle 60% of the time for business may deduct 60% of their car loan interest when reporting profit or loss from their business. Always consult a tax professional to ensure proper documentation and eligibility.
Car Loan Interest vs. APR
As you shop for auto loans, in addition to interest rate, you may also see the annual percentage rate (APR) listed. These two numbers are usually pretty close together, but APR can give you more information about how much you’ll actually owe over the life of your loan.
While the interest rate is a percentage that shows you how much you will pay to borrow alone, APR is a percentage that shows you your interest rate plus any other fees you might owe. APR illustrates total costs for financing a vehicle. The federal Truth in Lending Act generally requires that all lenders disclose APR, which can make it a good metric to use when comparing the true cost of borrowing as you shop for a loan.
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What Determines Interest Rates on Car Loans?
There are a variety of factors that may influence a lender’s auto loan interest rate offers. We highlight some of these factors below:
Type of Lender
Some lenders, particularly captive finance companies, may offer 0% APR on new car loans for a certain number of years. The following lenders may offer their best rate to borrowers with excellent credit:
• Banks
• Credit unions
• Buy here, pay here dealerships
• Independent finance companies
• Captive finance companies affiliated with auto manufacturers
New vs Used Financing
Used vehicles tend to carry higher interest rates than new cars. While the average interest rate for a new car loan was 7.1% during the first quarter of 2025, it was 11.3% for used cars.
Credit Score
Lenders may use your credit score as an indicator of how likely you are to pay down your debt on time. They see borrowers with higher scores as less risky and will typically offer them lower interest rates. In the first quarter of 2025, borrowers with the highest credit scores saw rates of 4.77% on average for new vehicle financing, while borrowers with the poorest credit scores saw interest rates of 15.75% on average.
Recommended: Does Financing a Car Build Credit?
Loan Term
Lenders see longer loan terms as riskier, so they may charge higher interest rates for them. This can lead to a phenomenon known as an upside-down loan. Cars generally depreciate quickly, and a long term and higher interest rate may mean you’ll eventually end up owing more on your loan than your car is worth.
Down Payment
A lender calculating car loan APR may offer you a lower interest rate based upon the size of your down payment. The more money you put down when you buy a car, the lower the interest rate a lender is likely to charge. It follows that the less money you put down, the more it will charge. That’s because your lender wants to balance the risk that you might default and leave them with a depreciated vehicle worth less than the amount you had left on your loan.
Interest Rate Environment
The interest rate environment can influence a lender’s decision-making concerning auto loan financing. When the Federal Reserve raises its fed funds rate target range to combat inflation, lenders may follow suit by raising their interest rates on consumer loans. Interest rates on consumer loans may be more affordable when the Federal Reserve lowers its fed funds target range to stimulate the economy.
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Average Car Loan Interest Rates
The average car loan interest rate will vary depending on a person’s credit score and loan term and whether they’re buying a new or used vehicle. Here’s a look at key data highlighted by Experian:
| Credit score | Average new car loan rate | Average used car loan rate |
|---|---|---|
| 781-850 (super prime) | 4.77% | 7.67% |
| 661-780 (prime) | 6.40% | 9.95% |
| 601-660 (near prime) | 9.59% | 14.46% |
| 501-600 (subprime) | 13.08% | 19.38% |
| 300-500 (deep subprime) | 15.75% | 21.81% |
Tips for Lowering Interest on Your Car Loan
If you want to pay less interest on your car loan, there are a few options that may help.
First, when you’re selecting a loan, you can choose one with a shorter term. Though this will increase the size of your monthly payments, you’ll pay less interest over the life of the loan.
Prepaying your loan can also reduce the amount of interest you pay if you have a simple interest loan. As you pay off your principal, the amount of interest you pay will get smaller faster.
Just look into whether your loan carries any prepayment penalties. Even if it does, you might be able to save money by paying your loan, or part of your loan, early.
You might also consider refinancing your loan, especially if interest rates drop or you build your credit score. When you refinance, you can pay off your old loan with a new loan that hopefully offers you a term or interest rate that better fits your needs.
Recommended: What Credit Score Is Used for Refinancing?
The Takeaway
Once you understand how interest is calculated, the factors that can affect it, and how it differs from APR, you’re in a better position to compare auto loans and find the one that’s right for you. You’ll also have a better sense of the strings you can pull if you ever want to pay less interest on your loan, whether by prepayment or refinancing.
If you’re seeking auto loan refinancing, SoFi is here to support you. On SoFi’s marketplace, you can shop and compare financing options for your car in minutes.
FAQ
Is car loan interest tax deductible?
Car loan interest is tax-deductible in limited cases. Traditional employees generally can’t deduct interest paid on a car loan, but self-employed taxpayers may deduct car loan interest if they use the car for business purposes.
Does paying a car loan off early mean you pay less interest?
Yes, paying off a car loan early typically means you pay less interest overall. Since interest accrues over time, reducing the loan term cuts down the total amount paid. However, check for prepayment penalties, as some lenders charge fees that could offset your savings from early payoff.
Can you calculate car loan interest manually?
Yes, you can calculate car loan interest charges manually if you know the interest rate and the outstanding loan balance. This applies to simple interest car loans in which the interest you owe each month is a percentage based on your loan balance. Interest on a precomputed interest loan is calculated by the lender upfront.
What is the formula to calculate car loan interest?
The formula to calculate how much interest you owe when making a monthly payment on a simple interest car loan is (interest rate/number of payments per year) x loan balance. The interest rate is expressed as a decimal in this formula. For example, a 5% interest rate would be expressed as 0.05. Getting $25,000 in car loan financing with a 5% simple interest rate would include a $104.17 interest charge in the first monthly payment as calculated under this given formula.
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