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NCAA.com | March 14, 2021

The NCAA bracket S-curve, explained

How to pick a 15 vs. 2 upset in the NCAA tournament — if you dare

One thing will stand above the rest when it comes to how the selection committee places teams in the 2021 NCAA tournament bracket: the S-curve. You're going to hear about it a lot leading up to and even during the tournament. So what exactly is it?

Here's how it works:

  • Basically, the S-curve is about the overall seed list that is created by and then used by the selection committee when it comes to bracketing decisions.
  • It's called the S-curve because it snakes through the seeding list based on groupings for each seed (four No. 1 seeds, four No. 2 seeds, four No. 3 seeds all the way through to the field of 68). This means the No. 1 overall seed will get the "weakest" No. 2 seed — the No. 8 team on the overall seed list.
  • Every team is on the S-curve, from the No. 1 overall seed (and the top No. 1 seed) through the No. 68 overall seed (the last No. 16 seed).
  • In previous years, the committee used the S-curve to put the top four teams on the seed list in four separate regions. This expands to the rest of the field for 2021. For example, the No. 5 overall seed (thus the top No. 2 seed) will be put in the same region as the overall No. 4 — the final No. 1 seed.
  • For the 2021 tournament, the S-curve takes greater importance because the whole tournament will be in Indiana — so geography doesn't play as big of a role. Previously, geography played a major role in placement for the top four teams on the seed list in the four separate regions.

HISTORY: Browse every NCAA bracket since 1939 with stats and records | What is March Madness 

Want a slightly deeper dive into how exactly the S-curve works — and looks for the bracket? Here's an example using regions (called Region A, B, C, D for this purpose only):

  • Region A
    • No. 1 overall seed (on the 1-seed line)
    • No. 8 overall seed (on the 2-seed line)
    • No. 9 overall seed (on the 3-seed line)
    • No. 16 overall seed (on the 4-seed line)
  • Region B
    • No. 2 overall seed (on the 1-seed line)
    • No. 7 overall seed (on the 2-seed line)
    • No. 10 overall seed (on the 3-seed line)
    • No. 15 overall seed (on the 4-seed line)
  • Region C
    • No. 3 overall seed (on the 1-seed line)
    • No. 6 overall seed (on the 2-seed line)
    • No. 11 overall seed (on the 3-seed line)
    • No. 14 overall seed (on the 4-seed line)
  • Region D
    • No. 4 overall seed (on the 1-seed line)
    • No. 5 overall seed (on the 2-seed line)
    • No. 12 overall seed (on the 3-seed line)
    • No. 13 overall seed (on the 4-seed line)

This snaking process continues through the seed list for seeds 5 through 16.

It's important to note that, as in previous seasons, principles remain in place when it comes to teams from the same conferences. Here's an expert from the official bracketing principle release for the 2021 tournament:

  • Each of the top four teams selected from a conference shall be placed in different regions if they are seeded on the first four lines.
  • Teams from the same conference shall not meet before the regional final if they played each other three or more times during the regular season, to include the conference tournament.
  • Teams from the same conference shall not meet before the regional semifinals if they played each other twice during the regular season, to include the conference tournament.
  • Teams from the same conference may play each other as early as the second round if they played no more than once during the regular season, to include the conference tournament.
  • If possible, rematches of nonconference regular-season games should be avoided in the First Four and first round.

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