For a standard fixed-rate car loan with equal monthly payments, calculate the payment using the amount financed, the monthly interest rate, and the number of payments: M = L × i ÷ [1 − (1 + i)−n]. Here, M is the monthly principal-and-interest payment, L is the amount financed, i is the monthly interest rate as a decimal, and n is the total number of monthly payments.
What information do you need?
The formula estimates payments for a fixed-rate loan that is repaid in equal monthly installments. Gather these three inputs:
- Amount financed (L): the principal borrowed, not necessarily the vehicle’s sticker price.
- Monthly interest rate (i): for a nominal annual interest rate expressed as a decimal, a common estimate is the annual rate divided by 12.
- Number of monthly payments (n): for a term stated in years, multiply the years by 12.
For example, a 6% nominal annual rate becomes 0.005 per month: 0.06 ÷ 12. Enter rates as decimals, so 6% is 0.06.
How do you calculate the monthly payment?
- Identify the amount financed, monthly rate, and payment count.
- Substitute the values into M = L × i ÷ [1 − (1 + i)−n].
- Evaluate the expression to estimate the monthly principal-and-interest payment.
Example: If you finance $25,000 at a 6% nominal annual interest rate for 60 months, then i = 0.06 ÷ 12 = 0.005 and n = 60. The estimated payment is about $483.32 per month. This is an arithmetic example, not a current market-rate claim or lender offer. If the interest rate is zero, divide the amount financed by the number of payments instead.
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You can also use a loan payment calculator by entering the loan amount, APR, and term. Treat its result as an estimate until you confirm the contract’s terms and charges.
How do you find the amount financed?
Start with the negotiated vehicle price, then account for costs included in the loan. Subtract the down payment and trade-in credit, and include any remaining balance on a trade-in or other charges rolled into financing. The result may differ substantially from the sticker price. The Consumer Financial Protection Bureau’s guidance on car costs recommends considering upfront costs and amounts that reduce borrowing, while evaluating ongoing ownership expenses separately.
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Should you use the interest rate or APR?
The formula requires a periodic interest rate. APR is a broader borrowing-cost measure that includes fees, while the interest rate does not. As a result, APR and interest rate are not interchangeable inputs. When comparing loan offers, compare APR with APR rather than comparing one offer’s APR with another offer’s interest rate. The CFPB explains the distinction in its guide to interest rates and APR.
A payment calculated from an APR divided by 12 is an estimate: the contract’s payment schedule and fees can affect the actual disclosed costs. Check the lender’s Truth in Lending disclosures, which include payment and finance-charge information, before signing. See the CFPB’s explanation of auto-loan Truth in Lending disclosures.
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How do you estimate total payments and interest?
Under the same fixed-payment assumptions, multiply the monthly payment by the number of payments to estimate total scheduled payments. Subtract the amount financed from that total to estimate interest paid in this simplified calculation. Contract fees or other features can cause the lender’s disclosed finance charge to differ from this estimate.
How should you compare car loan offers?
Compare offers using the same amount financed, and look beyond the monthly payment. A longer term can reduce the scheduled monthly amount while increasing total borrowing cost because payments continue for longer. The CFPB notes that a shorter term reduces total loan cost in its auto-loan key terms guide.
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| What to compare | Why it matters |
|---|---|
| APR | Provides a broader measure of borrowing cost that includes fees; compare APR with APR. |
| Loan term | Determines how many monthly payments are scheduled and affects total cost. |
| Monthly payment | Shows the scheduled monthly principal-and-interest amount, but not the full cost of borrowing or owning the car. |
| Total interest or finance charge | Helps show borrowing cost over the loan; verify the lender’s disclosed figure and terms. |
| Total cost | Consider loan costs alongside the expenses of owning the vehicle. |
The CFPB’s guide to comparing auto-loan offers and car-buying cost guidance address these trade-offs. Before signing, review the lender’s disclosures and confirm the payment, term, APR, and finance charge.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Does the payment tell you what you can afford?
No. The formula estimates the loan payment, not the full cost of having a car. Include insurance, fuel, maintenance, and other ownership expenses when deciding how much to borrow. The CFPB’s car-cost guidance separates those expenses from the amount financed.
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