Calculate 2D:4D digit ratios from index and ring finger lengths for one or both hands, or solve the missing value from any two inputs.

Measure index and ring fingers from the basal crease to the tip, using the same method.

A descriptive length ratio. It does not measure hormone levels or diagnose health, personality, or sexual orientation.

Related Calculators

Digit Index Ratio Formula

The following formula is used to calculate the digit index ratio:

DIR = IL / RL

Variables:

  • DIR is the digit index ratio
  • IL is the length of the index finger (mm)
  • RL is the length of the ring finger (mm)

To calculate the digit index ratio, divide the length of the index finger by the length of the ring finger.

What is a Digit Index Ratio?

The digit index ratio, also known as the 2D:4D ratio, is the length of a person's index finger (second digit, 2D) divided by the length of their ring finger (fourth digit, 4D). It is a descriptive measurement studied in population research. A person's ratio does not measure hormone levels or diagnose health, personality, or sexual orientation. Comparisons depend on the hand, population and measurement method.

How to Calculate Digit Index Ratio?

The following steps outline how to calculate the Digit Index Ratio.

  1. First, measure the index finger (IL) from its basal crease to the tip, in millimeters.
  2. Next, measure the ring finger (RL) from its basal crease to the tip using the same method.
  3. Use the formula DIR = IL / RL to calculate the digit index ratio.
  4. Finally, report the ratio and measurement method. Any statistical comparison requires a reference matching the hand, population and method; the optional calculator comparison uses a supplied mean and standard deviation under a normal model.

Example Problem:

Use the following variables as an example problem to test your knowledge.

Index Finger Length (IL) = 65 mm

Ring Finger Length (RL) = 70 mm