It's not unusual for college students to graduate with a hefty student loan debt. But according to a new study, many don't know how much they owe -- and some aren't aware they owe anything at all.

Research done at Iowa State University found 40 percent of the students there underestimated their total debt, with 10 percent of those students underestimating the total amount owed by more than $10,000.

What's more, one out of every eight students with loan debt didn’t even know they'd borrowed money for their studies.

Those results may seem shocking, but Cynthia Needles Fletcher, a professor of human development and family studies at ISU, wasn't surprised. “You’re talking about people who, for them, borrowing is new,” she said, adding that the complexity of the college financial aid process and the fact that students accumulate debt over time makes it easy to lose track of what's owed.

The researchers said their findings show that financial counseling is needed to help students understand their borrowing, so this summer, ISU will begin emailing students with an accounting of their debt and what their estimated monthly payment will be after they graduate.

More From TSM Interactive