Car Interest Calculator
Print| Monthly Loan Payment | $0.00 / mo |
| Total Out-of-Pocket Payment | $0.00 |
Don’t let interest charges surprise you when purchasing a vehicle. Use this Car Interest Calculator to compute total finance charges, analyze monthly principal versus interest splits, and see how loan length and APR impact total auto repayment costs.
The Formula for Auto Loan Interest Calculation
Calculating the monthly payment and total accumulated interest on a simple-interest auto loan relies on the standard loan amortization formula:
Monthly Payment (PMT) = P × [r(1 + r)^n] / [(1 + r)^n - 1]
Total Loan Interest = (PMT × n) - P
Where:
- P: Financed vehicle principal loan amount (Purchase Price + Fees – Down Payment – Trade-in).
- r: Monthly interest rate (Annual APR divided by 12).
- n: Total loan term in months (e.g., 36, 48, 60, or 72 months).
Auto Loan Interest Cost by Term & APR Matrix
Refer to the lookup table below to see total interest charges for a $30,000 auto loan across common terms and interest rates:
| Loan Term | Interest Rate (APR) | Monthly Payment | Total Interest Paid | Total Paid over Life of Loan |
|---|---|---|---|---|
| 36 Months (3 Yrs) | 5.0% APR | $899 / month | $2,364 | $32,364 |
| 48 Months (4 Yrs) | 6.0% APR | $705 / month | $3,840 | $33,840 |
| 60 Months (5 Yrs) | 7.0% APR | $594 / month | $5,640 | $35,640 |
| 72 Months (6 Yrs) | 8.5% APR | $534 / month | $8,448 | $38,448 |
Step-by-Step Car Interest Calculation Example
Suppose you finance $25,000 for a used vehicle at 7.0% APR over a 60-month loan term:
- Convert Annual APR to Monthly Rate: 7.0% / 12 = 0.005833 per month.
- Calculate Monthly Loan Payment: Using the amortization formula, monthly payment PMT equals $495.03 per month.
- Calculate Total Loan Payments: $495.03 × 60 months = $29,701.80 total lifetime outlay.
- Subtract Financed Principal: $29,701.80 – $25,000 = $4,701.80 total auto loan interest paid.
Frequently Asked Questions
Are car loans calculated with simple interest or compound interest?
Most auto loans use simple interest calculated daily based on your remaining principal balance, meaning paying extra principal early directly reduces total interest paid.
How does credit score affect car loan interest rates?
Borrowers with super-prime credit scores (780+) typically qualify for rates between 4% and 6%, while subprime borrowers (under 600) may face auto APRs ranging from 12% to 20% or higher.
Can I lower my total car interest by refinancing?
Yes, if market interest rates drop or your credit score improves after purchase, refinancing your auto loan into a lower APR or shorter term can save thousands in interest charges.
Is interest tax-deductible on a personal auto loan?
No, interest paid on personal auto loans is not tax-deductible. However, if the vehicle is used for qualified business purposes, a portion of the interest may be deductible as a business expense.