The cost of attending college today is a daunting prospect. According to the College Board’s 2018 Trends in College Pricing Report, from 1988 to 2018, sticker prices tripled at public four-year schools and doubled at public two-year and private non-profit four-year schools, and many students use some kind of student loan to finance their degrees.

In 2009 Americans owed just over $700 million in student debt. Today, Americans owe nearly $1.6 trillion.

But Michael B. Horn, co-founder of the Clayton Christensen Institute, tells CNBC Make It that there’s a simple way students can predict roughly how much they can afford to borrow for college.