is the second digit your index finger
Scientists have long noticed that menâs ring fingers are generally longer than their index fingers. With women, it tends to be the reverse: their index fingers are usually longer. 2D stands for âsecond digitâ â thatâs your index finger, and 4D means âfourth digitâ â your ring finger. So if your index finger is 2.9 inches long and your ring finger is 3.1 inches long, you have a 2D:4D ratio of .935 (2.9/3.1 = .935).