This is where a good auto loan calculator comes in handy. There isn’t a set monthly payment amount for a $30,000 auto loan. Instead, your set interest rate and the length of your loan will determine just how much you pay to the lender each month. Your lender will choose your interest rate based on your credit history. The rate you receive can shift several points in either direction depending on the financial climate. But if we use those numbers as our goal lines, you can get a pretty solid idea of how interest affects your monthly payment. For example, a $30,000 auto loan with a 60-month (five years) repayment window and a 4.23% interest rate will yield a $556 monthly payment. That same loan with a 14.70% interest rate will cost you a whopping $709 each month. Your loan term also affects your monthly payment. Your term is how much time you have in which to pay the loan off. The longer your term, the smaller your monthly payments. That sounds like a better deal, but there’s a trade-off. In return for those smaller monthly payments, you’ll pay a good bit more in interest. All interest charges compound monthly. The more months you add to your loan, the more money you’ll pay to satisfy the debt payment.