Autokreditrechner — Formel

How Auto Loan Payments Work

An auto loan uses the same amortization formula as a mortgage, just with shorter terms and smaller amounts. You borrow the purchase price minus your down payment, and pay it back in equal monthly installments over 3-7 years. Each payment covers interest on the remaining balance plus a chunk of principal.

The Formula

Monthly Payment = P * [r(1+r)^n] / [(1+r)^n - 1]

P = Amount financed (vehicle price minus down payment minus trade-in value)

r = Monthly interest rate (APR / 12 / 100)

n = Number of monthly payments

When to Use This

Before visiting a dealership. Know what your monthly payment will be at different price points so you negotiate on total price, not monthly payment. Dealers love to stretch the term to make any car look affordable. A $35,000 car at 6% for 72 months is $580/month. The same car for 48 months is $822/month, but you save $3,700 in interest.

What Changes the Payment Most

Loan term has the biggest impact on monthly payment. APR has the biggest impact on total cost. A 2% rate difference on a $30,000 loan over 60 months adds about $1,600 in total interest. Your credit score directly determines your rate: 750+ gets you 4-5%, 650-700 gets you 7-9%, below 600 can mean 12%+.

The Hidden Cost of Long Terms

A 72 or 84-month loan keeps payments low but creates a dangerous situation: you owe more than the car is worth for most of the loan. Cars depreciate 15-20% in year one. On a 72-month loan with minimal down payment, you could be $5,000-$8,000 underwater after two years. If you total the car or need to sell, you still owe the difference.

Common Mistakes

Negotiating based on monthly payment instead of total price. The dealer can hit any monthly number by extending the term.

Forgetting taxes, registration, and dealer fees. These add 8-12% to the purchase price in most states and are often rolled into the loan.

Skipping pre-approval from your bank or credit union. Dealer financing is convenient but typically 1-2% higher than what you can get on your own.