Car Payment Calculator: Monthly Auto Loan Payment Formula
Quick Answer
- *Monthly payment formula: M = P × [r(1+r)^n] / [(1+r)^n − 1] where P = loan amount, r = monthly rate (APR/12), n = months.
- *A $28,000 loan at 7% APR for 60 months costs approximately $554/month and $5,240 in total interest.
- *Average monthly payments per Experian Q3 2024: ~$735 new, ~$525 used.
- *The 20/4/10 rule: 20% down, finance ≤4 years, total vehicle costs ≤10% of gross monthly income.
The Monthly Car Payment Formula
Every auto loan payment is calculated using the standard amortization formula. It looks complicated at first, but the logic is straightforward: you're spreading the loan principal plus interest evenly across a fixed number of payments.
M = P × [r(1+r)^n] / [(1+r)^n − 1]
Where:
- M = monthly payment
- P = principal (loan amount after down payment)
- r = monthly interest rate (APR ÷ 12)
- n = total number of monthly payments (years × 12)
The formula ensures each payment covers that month's interest first, with the remainder reducing the principal. Early payments are mostly interest. Later payments are mostly principal. This is called amortization.
Worked Example: $28,000 Loan at 7% APR, 60 Months
Let's walk through a real calculation. You finance $28,000 at 7% APR for 5 years (60 months).
- r = 0.07 ÷ 12 = 0.005833 (monthly rate)
- n = 60 months
- (1.005833)^60 = 1.4176
Plugging in: M = $28,000 × [0.005833 × 1.4176] / [1.4176 − 1]
M = $28,000 × [0.008269] / [0.4176]
M = $28,000 × 0.01980
M = ~$554/month
Total paid = $554 × 60 = $33,240
Total interest = $33,240 − $28,000 = $5,240
You don't need to run this math by hand. Our car payment calculator handles it instantly.
Loan Term Comparison: Same Loan, Different Terms
Stretching out your loan term lowers your monthly payment but dramatically increases what you pay in interest. Here's how the numbers shake out on that same $28,000 at 7% APR:
| Loan Term | Monthly Payment | Total Paid | Total Interest |
|---|---|---|---|
| 36 months (3 yr) | $864 | $31,104 | $3,104 |
| 48 months (4 yr) | $670 | $32,160 | $4,160 |
| 60 months (5 yr) | $554 | $33,240 | $5,240 |
| 72 months (6 yr) | $477 | $34,344 | $6,344 |
| 84 months (7 yr) | $426 | $35,784 | $7,784 |
Going from 36 to 84 months cuts your payment by $438/month. But it costs an extra $4,680 in interest. And that's before factoring in the risk of being underwater on the loan — owing more than the car is worth — which is common on long-term loans as the car depreciates faster than you pay it down.
Down Payment Impact
Your down payment directly reduces the amount you finance. More down = smaller principal = lower payment and less total interest. Here's a concrete example on a $35,000 car at 7% APR over 60 months:
| Down Payment | Amount Financed | Monthly Payment | Total Interest |
|---|---|---|---|
| 10% ($3,500) | $31,500 | ~$623/month | ~$5,895 |
| 20% ($7,000) | $28,000 | ~$554/month | ~$5,240 |
| 30% ($10,500) | $24,500 | ~$485/month | ~$4,585 |
Going from 10% to 20% down saves about $69/month and over $655 in total interest over the life of the loan. It also gives you immediate equity in the vehicle, which matters a lot if you need to sell or trade in early.
APR Rate Impact
Your credit score is the biggest lever on your APR. Even a 2% difference in rate can cost or save thousands over the loan term. Here's the same $28,000 loan over 60 months at different APRs:
| APR | Monthly Payment | Total Interest Paid |
|---|---|---|
| 4% | $516 | $2,960 |
| 6% | $541 | $4,462 |
| 8% | $568 | $6,074 |
| 10% | $595 | $7,700 |
The difference between 4% and 10% APR is $79/month and $4,740 in total interest over 5 years. Improving your credit score before applying — even by 20–30 points — can move you into a better rate tier and save real money.
New vs. Used Car Loan Rates
New cars typically carry lower APRs than used cars. Lenders view new cars as lower risk collateral since the value is known and dealer-certified. According to Experian's 2024 State of the Automotive Finance Market:
- New car average APR: ~7.1%
- Used car average APR: ~11.7%
That 4.6% gap is substantial. On a $28,000 loan over 60 months, the difference between 7.1% and 11.7% APR is roughly $68/month and over $4,000 in total interest. Used cars may have a lower sticker price, but the higher rate partially offsets that savings advantage.
Average Monthly Car Payment (2024)
Wondering how your payment compares? Per Experian's Q3 2024 automotive finance data:
- New car average monthly payment: ~$735/month
- Used car average monthly payment: ~$525/month
These averages include buyers across all credit tiers and loan terms. If your payment is significantly above these numbers, it's worth revisiting your loan term, down payment, or the vehicle price itself.
The 20/4/10 Rule
Personal finance experts have long recommended the 20/4/10 rule as a quick affordability check before buying a car:
- 20% down: Put at least 20% down to build immediate equity and avoid being underwater.
- 4 years max: Finance for no more than 4 years (48 months). Longer terms mean more interest and more risk.
- 10% of gross income: Total monthly vehicle costs — payment, insurance, and gas — should be ≤10% of your gross monthly income.
On a $6,000/month gross income, that means total car costs should stay under $600/month. With insurance averaging $150–$200/month and gas at $100–$150/month, that leaves $250–$350/month for the actual loan payment — which points toward a vehicle in the $15,000–$20,000 range, not $40,000.
The 20/4/10 rule is conservative but time-tested. It prevents the common trap of stretching into a 72- or 84-month loan to make a more expensive car “affordable.”
GAP Insurance: Why It Matters
GAP (Guaranteed Asset Protection) insurance covers the difference between what you owe on the loan and what your car is worth if it's totaled or stolen. It's especially important in the first two years of ownership.
Here's why: new cars depreciate 15–20% in the first year. If you financed $35,000 with 10% down and the car loses $7,000 in value in year one, you could owe $28,000 while the car is only worth $25,000. Standard auto insurance only pays market value — that $3,000 gap comes out of your pocket without GAP coverage.
GAP insurance typically costs $200–$400 as a one-time add-on through your lender, or $20–$40/year through your auto insurer. It's worth it if you put less than 20% down or are financing for longer than 48 months.
Total Cost of Ownership
The monthly payment is only one piece of what a car actually costs. The real number that matters is total cost of ownership (TCO) over the years you keep the vehicle:
- Loan payments: Principal + interest (calculated above)
- Insurance: Average $150–$250/month depending on coverage, age, and location
- Gas: Average $100–$200/month depending on mileage and fuel type
- Maintenance: Oil changes, tires, brakes — typically $1,000–$1,500/year for routine service
- Depreciation: New cars lose 15–20% of value in year one, 10–15% in subsequent years
A $35,000 new car with a $600/month payment might cost $900–$1,100/month in total operating expenses. After five years, the car may be worth $12,000–$15,000 while you've spent $60,000–$65,000 keeping and paying for it. Understanding this full picture helps you decide between new vs. used, leasing vs. buying, and how much to spend.
Calculate your exact monthly payment
Use our free Car Payment Calculator →Also compare options with our Auto Loan Best Deal Guide
Frequently Asked Questions
How do you calculate a monthly car payment?
Use the standard loan amortization formula: M = P × [r(1+r)^n] / [(1+r)^n − 1], where P is the loan principal, r is the monthly interest rate (APR divided by 12), and n is the number of monthly payments. For a $28,000 loan at 7% APR over 60 months, the monthly payment works out to approximately $554. You can skip the math entirely with our car payment calculator.
How much car can I afford?
The 20/4/10 rule is a widely used guideline: put at least 20% down, finance for no more than 4 years, and keep total vehicle costs (payment + insurance + gas) at or below 10% of your gross monthly income. On a $6,000/month gross income, that means total car costs should stay under $600/month. Most financial planners recommend keeping the car payment itself under 15% of your take-home pay.
How does the loan term affect car payments?
A longer loan term lowers your monthly payment but significantly increases total interest paid. On a $28,000 loan at 7% APR, a 36-month term costs $864/month but only $3,104 in total interest. An 84-month term drops the payment to $426/month but costs $7,784 in total interest — more than double. Longer terms also increase the risk of being underwater on the loan as the car depreciates faster than you pay it down.
What is APR on a car loan?
APR (Annual Percentage Rate) is the yearly cost of borrowing, expressed as a percentage. It includes the interest rate plus any origination fees or dealer markups, making it a more accurate measure of the true loan cost than the stated interest rate alone. According to Experian's Q3 2024 data, average APRs were 7.1% for new cars and 11.7% for used cars. Your actual APR depends heavily on your credit score — borrowers with scores above 720 typically qualify for the lowest rates.
Should I put more money down on a car?
Generally yes. A larger down payment reduces your loan principal, which lowers both your monthly payment and total interest paid. It also reduces the risk of being underwater on the loan. On a $35,000 car, going from 10% down ($3,500) to 20% down ($7,000) reduces your financed amount from $31,500 to $28,000 — saving roughly $69/month and over $655 in total interest over 60 months at 7% APR. The main exception is when the cash could earn a higher return elsewhere, such as paying off high-interest debt.