How do I calculate the interest that I would have to pay over the life of a loan if I take out a 5 year 20000 dollar car loan at 9% a year? I know that I pay monthly at the rate of $415.17. 2. ## Re: Loan Amoritization Hello, Eraser147! No fancy formulas required . . . How do I calculate the interest that I would have to pay over the life of a loan if I take out a 5-year$20,000 car loan at 9% a year? .I pay $415.17 monthly. You borrowed$\displaystyle \$20,\!000.$
You pay back $\displaystyle \$415.17$per month for$\displaystyle 60$months. You pay back a total of:$\displaystyle 60 \times \$415.17 \:=\:\$24,\!910.20$Therefore, the interest is:$\displaystyle \$24,\!910.20 - 20,\!000 \:=\:\$4,\!910.20\$