NCAA Tournament upsets come in all shapes and sizes. Mid-majors take down major conference opponents. Underdog majors take down higher seeds. And even title favorites fall victim to lesser-known contenders from time to time.

A lot of people out there have a certain set of criteria when determining how big an upset actually is. Maybe the Cinderella team has to be a double-digit seed or maybe they have to be so many seeds lower than the favorite. Some go off Vegas odds alone. No matter what you think qualifies as an upset, we here at numberFire have a better way to determine which upsets are truly the biggest.

Our nERD metric measures the number of points we'd expect a team to win by against an average squad on a neutral court. For example, a team with a nERD of 12.0 would be expected to beat a team with a nERD of 7.5 by an estimated 4.5 points on a neutral court, like in the NCAA Tournament.

Using this metric, we can go through the bigger upsets, by seeding, and rank them by their difference in nERD. Meaning, the team with the biggest nERD deficit pulled the most surprising upset.

Since there have been no 1-16 upsets in tournament history, we'll look to the 24 total 2-15, 3-14, and 4-12 upsets over the last 17 seasons. Of them, here are the five biggest upsets by nERD.