# Odds vary for perfect March Madness bracket

Picking the winner of the annual NCAA men’s basketball tournament is difficult enough.

Trying to pick the entire bracket correctly is next to impossible.

How improbable?

Odds range all over the place, and exact odds would change every year based on the likelihood of individual teams advancing. Following the First Four — games typically excluded from brackets — the tournament features 63 games.

Correctly predicting a coin flip 63 times in a row happens one in every 9.2 quintillion opportunities. One quintillion is not a made up number, though the odds of hitting it might as well be fictional. One quintillion is one billion billions.

The odds of choosing five individual numbers between 1 and 59 — the numbers used in the lottery — are one in 175 million.

But the coin flip analogy assumes that with every flip there is an equal chance of getting heads as there is to getting tails. The assumption, though logical, is not the way tournament games pan out in terms of probability.

A 16th-seeded team, for example, has never beaten a top seed, so the odds of such an outcome are far from 50-50. Assuming the four first-round games all go as predicted, the odds “drop” to 1 in 57.6 quadrillion. A quadrillion is “only” a million billions, so still practically impossible but significantly better.

If all four 2-seeds beat 15 seeds in their first games along with top seeds beating 16 seeds, the number drops further — odds are only one in 3.6 quadrillion.

But seven teams seeded 15th have won at least one game in the NCAA tournament. Calculating odds along the way becomes a difficult challenge.

Experts quoted by FiveThirtyEight.com estimated that the actual odds when all the odds of individual games are accounted for are anywhere from one in 5 billion to one in 135 billion — so numbers that people actually have used.

Under the best circumstances, a person would win the lottery 28.5 times before correctly predicting all 63 outcomes of the standard NCAA tournament bracket.