Heads or Tails? Evidence Shows Probability Isn't 50%—Here's How to Improve Your Odds

Think flipping a coin is pure chance? Think again. Recent research suggests that by calling the side that is facing up before the toss, you can increase your odds of winning.


Researchers conducted 350,757 coin flips and found that the initial side of the coin, the one facing up before the flip, tends to land facing up again slightly more often. Frantisek Bartos from the University of Amsterdam in the Netherlands noted that this technique gives you a winning chance of 50.8%.

This work builds on a 2007 study led by Persi Diaconis, a mathematician at Stanford University. Diaconis had suggested that a slight imbalance is introduced when a coin is flipped with the thumb, due to "pitch" and a slight tilt. Frantisek Bartos has confirmed this theory. According to the researchers, the coin lands on the initial side 51% of the time.

The effect isn't uniform across all tossers. Some flippers show a much higher success rate than the 50.8% average observed. Furthermore, this phenomenon does not occur if one randomly chooses heads or tails before each flip. Moreover, it is not dependent on the coin: none of the 46 different currencies tested showed any sign of bias.

To eliminate any advantage, simply ensure that the person calling "heads" or "tails" cannot see the starting side of the coin before the toss. Frantisek Bartos points out that this finding could have implications in various fields, including gambling and sports.