2d4

2d4 is a common dice notation used in tabletop role-playing games and board games to indicate rolling two four-sided dice and summing their results. Each die is a d4, a tetrahedral die with faces numbered from 1 to 4.

The sum of two d4 rolls can range from 2 to 8. Across the 16 equally likely outcomes (4 faces on each die), the counts for each total are: 2 (1 way), 3 (2 ways), 4 (3 ways), 5 (4 ways), 6 (3 ways), 7 (2 ways), 8 (1 way). Therefore the probabilities are: 2 and 8: 1/16; 3 and 7: 2/16 (1/8); 4 and 6: 3/16; 5: 4/16 (1/4). The expected value is 5; the variance is 2.5 and the standard deviation is about 1.58.

Usage and context: In many role-playing games, 2d4 is used to determine damage, healing, or other effects. It provides a wider range of possible results than a single d4 and yields a distribution that concentrates around the middle totals (with a peak at 5), offering more mid-range outcomes.