How Car Payments Are Calculated
Every auto loan uses the standard amortization formula: M = P × [r(1+r)n] / [(1+r)n – 1], where M is your monthly payment, P is the loan amount (vehicle price + sales tax – down payment – trade-in), r is the monthly interest rate (APR ÷ 12), and n is the total number of payments.
On a $35,000 car at 6.5% APR for 60 months, your monthly rate is 0.5417% (6.5% ÷ 12). The formula yields $685/month. Over 60 months you pay $41,078 total—that's $6,078 in interest on top of the $35,000 principal.
Early in the loan, more of each payment covers interest. By the midpoint, the split roughly reverses. This is why paying extra in the first year has the biggest impact—you reduce the balance that future interest compounds on.
New vs Used Car Financing
Interest rates, depreciation, and total cost differ significantly between new and used vehicles. Here's how they compare in 2026:
| Factor | New Car | Used Car (3–5 years old) |
|---|---|---|
| Typical APR | 4% – 7% | 6% – 11% |
| Common Terms | 48 – 72 months | 36 – 60 months |
| Year 1 Depreciation | 15% – 25% | 10% – 15% |
| Warranty Coverage | Full manufacturer warranty | May be expired or limited |
| Example: $30K vehicle | $561/mo @ 5.5% / 60mo | $608/mo @ 8.5% / 60mo |
| Total Interest Paid | $3,664 | $6,497 |
New cars get lower rates because the vehicle is worth more as collateral. But a 3-year-old used car has already absorbed the steepest depreciation. The sweet spot for value: a certified pre-owned (CPO) vehicle that's 2–3 years old with remaining factory warranty coverage and a rate under 7%.
5 Ways to Lower Your Car Payment
- Increase your down payment. Putting $5,000 down on a $35,000 car at 6.5% for 60 months drops your payment from $685 to $588/month and saves $1,015 in interest. Aim for at least 20% down to avoid being underwater on the loan.
- Shorten your loan term. A 48-month loan at 6.5% on $30,000 costs $711/mo vs $588/mo for 60 months, but you save $1,468 in total interest. Choose the shortest term you can comfortably afford.
- Improve your credit score before buying. The difference between a 650 and 750 credit score can mean 3–5 percentage points in APR. On a $30,000 loan, that's $50–$80/month. Pay down credit cards and dispute errors 3–6 months before shopping.
- Get pre-approved from your bank or credit union. Dealer financing is convenient but often marked up 1–2% above what you qualify for. Walk in with a pre-approval letter and use it as leverage. Credit unions consistently offer the lowest auto rates.
- Maximize your trade-in value. Clean the car, fix minor cosmetic issues, and get quotes from Carmax, Carvana, and local dealers before negotiating. A $2,000 higher trade-in value saves you $39/month on a 60-month loan.
For other types of loans, use our loan payment calculator. To see how a home loan breaks down with taxes, insurance, and PMI, try the mortgage calculator. And to check whether your car payment fits your overall budget, run the affordability calculator.