Look at the difference in length between your second (index or pointer) finger and your fourth (ring) finger. That difference is called the digit ratio. It's calculated by dividing your second finger length by your fourth finger length. AncestryDNA^® + Traits can tell you if your DNA suggests your index finger may be longer than your ring finger—or vice versa.

Index to Ring Finger Ratio

Most often the index finger is shorter than the ring finger in both males* and females*. But if you look across any population, you'll see variation. Some people have longer fourth fingers while others do not. Why is that?

Some of the variation in ratios is due to genetics. So a significantly longer ring finger for instance could be partly due to the DNA you get from your biological parents.

Your digit ratio may also be related to the relative levels of testosterone and estrogen you were exposed to in the womb. Developing fetuses that experience greater testosterone exposure usually have smaller digit ratios. This is why males, who tend to be exposed to more testosterone in the womb, often have smaller digit ratios.

Genetics of Your Finger Length

Some studies have estimated that genes are responsible for about 60% of the variation in finger length from one person to the next. Two of these genes are the SMOC1 gene on chromosome 14 and the LIN28B gene on chromosome 6.

Both the SMOC1 gene and the LIN28B gene are involved in early limb development, and DNA differences in these genes may help determine your digit ratio.

So how does genetics relate to other factors that impact finger length, like estrogen or testosterone hormone levels? Scientists are still trying to determine whether it's the genes that are controlled by hormone levels, or the hormones that control the genes.

What Else Does Science Say About Your Finger Length?

Aside from genetics, is there a connection between how long your ring finger and index finger are and other factors? Does finger length have any bearing on how good you are at sports? Or how good your sense of direction is?

Though not without controversy, numerous studies have looked for connections between your digit ratio and other characteristics and conditions. And in some of these studies, the digit ratio has been shown to have a correlation with a wide range of conditions and traits including, obesity, attention deficit disorder, autism, prostate cancer, visuo-spatial ability (sense of direction), athletic performance, and more. Scientists are still trying to understand how strong these correlations are, and what actually causes them (hint: it’s probably not the digit ratios themselves).

Interesting Facts About Your Digit Ratio

If you're a twin, there's another twist to how much longer (or shorter) your ring finger is compared to your index finger: the gender of your twin. Females with male twins will have a longer ring finger than they might have had otherwise, thanks to their male twin's testosterone that they were exposed to in the womb.

And the digit ratio you have today is probably the same one you were born with. This is because as you develop into adulthood, your limbs tend to grow by the same proportions. So even though both your index finger and ring finger got longer, they both got longer by about the same amount.

*Assigned sex at birth

References

Bergland, Christopher. “The neuroscience of finger length and athletic prowess.” Psychology Today. October 14, 2016. https://www.psychologytoday.com/us/blog/the-athletes-way/201610/the-neuroscience-finger-length-ratio-and-athletic-prowess.

Collaer, Marcia L., Stian Reimers. John T. Manning. “Visuospatial performance on an internet line judgment task and potential hormonal markers: sex, sexual orientation, and 2D:4D.” Archives of Sexual Behavior. June 2007. https://pubmed.ncbi.nlm.nih.gov/17380373/.

Hines, Melissa, Mihaela Constantinescu, Debra Spencer. “Early androgen exposure and human gender development.” Biology of Sex Differences. February 2015. https://pubmed.ncbi.nlm.nih.gov/25745554/.

Jeevanandam, Saravanakumar, Prathibha K Muthu. “2D:4D Ratio and its implications in medicine.” Journal of Clinical and Diagnostic Research. December 2016. https://pubmed.ncbi.nlm.nih.gov/28208851/.

Lawrance-Owen, Adam J., Gary Bargary, et al. “Genetic association suggests that SMOC1 mediates between prenatal sex hormones and digit ratio.” Human Genetics. April 2013. https://pubmed.ncbi.nlm.nih.gov/23263445/.

Leslie, Mitch. “Talk to the hand. Scientists try to debunk idea that finger length can reveal personality and health.” Science. June 6, 2019. https://www.science.org/content/article/talk-hand-scientists-try-debunk-idea-finger-length-can-reveal-personality-and-health.

Medland, Sarah E. Tetyana Zayats, et al. “A variant in LIN28B is associated with 2D:4D finger-length ratio, a putative retrospective biomarker of prenatal testosterone exposure.” The American Journal of Human Genetics. April 9, 2010. https://pubmed.ncbi.nlm.nih.gov/20303062/.

Weinberg, Seth M., Parsons Trish E., et al. “Prenatal sex hormones, digit ratio, and face shape in adult males.” Orthodontics & Craniofacial Research. February 2015. https://pubmed.ncbi.nlm.nih.gov/25257381/.