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Car Loan Interest and Monthly Payments Explained
A $28,000 car loan at 5.9% APR for 60 months has an estimated monthly payment of $541 and costs approximately $4,441 in total interest. The loan term you choose changes both numbers significantly, and so does your credit score. Here is the math.
The car loan payment formula
Car loans use the same amortization formula as mortgages:
\[M = P \times \frac{r(1+r)^n}{(1+r)^n - 1}\]Where M is the estimated monthly payment, P is the loan principal (amount financed), r is the monthly interest rate (annual rate divided by 12), and n is the total number of monthly payments. Each payment covers some interest and some principal. Early payments are mostly interest, and later payments are mostly principal, following the same amortization pattern as any fixed-rate loan.
Worked example: $28,000 at 5.9% APR
With a loan amount of $28,000 and a monthly rate of 0.004917 (5.9% / 12), the estimated monthly payment for a 60-month term is approximately $540. Total paid over 60 months is $32,400, meaning approximately $4,400 goes to interest. The car loan calculator runs this formula for any combination of amount, rate, and term.
A second example: $18,000 at 7.2% APR
Not every car purchase involves a $28,000 loan. Consider a used car financed at $18,000 with a 7.2% APR for 48 months. The monthly rate is 0.006 (7.2% / 12). Plugging into the formula, the estimated monthly payment is approximately $433. Over 48 months, you pay a total of $20,784, meaning approximately $2,784 goes to interest. Even though the rate is higher than the first example, the total interest is lower because the principal is smaller and the term is shorter. Both variables matter. The car payment calculator lets you adjust all three inputs to see how they interact.
How loan term affects your payment and total cost
Shorter loans have higher monthly payments but lower total interest. Longer loans are more affordable each month but cost more overall. The tradeoff is real: the monthly difference is substantial, but so is the total interest difference.
| Term | Estimated monthly payment | Total interest paid | Total cost |
|---|---|---|---|
| 36 months | $851 | $2,631 | $30,631 |
| 48 months | $656 | $3,499 | $31,499 |
| 60 months | $540 | $4,400 | $32,400 |
Going from a 36-month to a 60-month term saves approximately $311 per month, which matters for monthly budgeting. But you pay an estimated $1,769 more in total interest over the life of the loan. The right choice depends on your monthly cash flow and whether you can comfortably handle the higher payment. Use the car payment calculator to compare different terms.
How a down payment reduces total cost
A down payment reduces the loan principal, which reduces both your monthly payment and total interest. On a $32,000 car with a $4,000 down payment, you finance $28,000 (the example above). Without a down payment, you finance the full $32,000 at 5.9% for 60 months, which produces an estimated payment of $617 per month and approximately $5,029 in total interest.
The $4,000 down payment saves approximately $629 in interest over 60 months, on top of lowering every monthly payment by $77. Larger down payments also reduce the risk of owing more than the car is worth. Cars depreciate quickly in the first few years, and financing 100% of the purchase price makes it more likely the loan balance will exceed the car’s resale value during that period. This is sometimes called being “underwater” on the loan. Putting 10% to 20% down provides a buffer against that depreciation.
How credit score affects your rate
The APR you receive depends heavily on your credit score, and the difference in total cost can be thousands of dollars. Here are approximate average rates for new car loans (2025 data):
| Credit score range | Approximate APR |
|---|---|
| 750+ (Excellent) | 5.0%–6.0% |
| 700–749 (Good) | 6.5%–8.0% |
| 650–699 (Fair) | 9.0%–11.0% |
| Below 650 (Poor) | 12.0%–18.0%+ |
On a $28,000 loan for 60 months, the difference between 5.9% and 11% APR is an estimated $68 per month and approximately $4,102 in additional interest over 5 years. That means credit score alone can change the total cost of the car by more than $4,000. For borrowers with lower scores, a shorter loan term or larger down payment can help offset the higher rate. The math works the same way for simple vs. compound interest calculations; the rate and time are the two variables with the biggest impact.
Common mistakes when financing a car
One frequent error is focusing only on the monthly payment and ignoring total cost. A dealer might offer a low monthly number by stretching the term to 72 or 84 months. On a $28,000 loan at 5.9%, extending from 60 months to 72 months drops the monthly payment from approximately $540 to $464, but total interest rises from approximately $4,400 to $5,408. That extra year of payments costs over $1,000 in additional interest.
Another mistake is forgetting that the interest rate applies to the amount financed, not the sticker price. Taxes, fees, and add-ons rolled into the loan increase the principal and therefore the total interest. A $28,000 car with $3,000 in taxes and fees financed at 5.9% for 60 months has an estimated payment of approximately $600, not $540. Keeping those costs separate or paying them upfront avoids compounding interest on money that did not go toward the car itself.