A ring finger longer than the index finger is normal, and so is the opposite. Researchers call this comparison 2D:4D, the second digit over the fourth, and it became famous because of what it was proposed to reveal about hormones before birth. That claim is much shakier than the headlines suggest.
You probably got here after a video or an article told you what your fingers say about you. Here is what is known, with the study behind each claim, and a measurement you can take yourself. It tells you about your fingers. It doesn't tell you about you.
Your ratio
Your ratio is one length divided by another: index over ring. Below 1, your ring finger is longer. Above 1, your index is. Very near 1, they're about equal, and the tool says so instead of picking a winner.
From a camera or a photo it is an estimate, and the tool labels it as one right beside the number. We measured how much it moves: across repeat photos of one hand the spread was about 0.015, against about 0.031 between different people, around a typical reading of 0.976. So one hand between photos moves about half as far as one person differs from the next. Here is why that matters.
The whole gap between the average man and the average woman in the study that started this was 0.02. Our camera's wobble on one hand is nearly that size. So if you scan twice and get 0.98 and then 0.99, nothing happened. A ruler at home isn't a cure, either: self-measured reliability in one big internet study was estimated at 46% of expert-measured. Researchers themselves use calipers, photocopies and X-rays, and a 2021 review cited by Wikipedia worries that this leaves room to report only the measurements that came out significant.
How 2D and 4D are measured
The research standard is on the palm side, "from the midpoint of the bottom crease to the tip of the finger". Our camera doesn't look for that crease. It adds up the segments between the joints the hand model finds, starting from the knuckle joint, which sits inside the palm below the crease. Both are fair ways of getting a length. They just aren't the same length, which is why our number is not directly comparable with the studies, and why the ruler option is there.
- Use your right hand, palm up and relaxed, with the fingers straight.
- Find the crease where each finger meets the palm. If there are two, the research uses the lower one, closest to the palm.
- Measure the index and ring fingers from the middle of that crease to the fingertip, to the nearest millimetre. Don't count the nail.
- Divide the index length by the ring length. Below 1 means the ring finger is longer.
- Measure both fingers again on another day, and see how much your own number moves.
A worked example: index 72 mm, ring 75 mm. 72 ÷ 75 = 0.960, so the ring finger is longer. The ruler option above does this division for you and draws your result.
What's actually established
One thing has held up fairly well. On average, men's ratios are a little lower than women's. John Manning's 1998 paper reported a mean of 0.98 in men and 1.00 in women, and that the difference shows by about age 2. A 2010 meta-analysis by Honekopp and Watson calls it "a moderate sex difference", larger on the right hand, with "substantial heterogeneity", meaning results vary a lot between studies.
That is a statement about averages. Averages only 0.02 apart leave the two groups overlapping heavily, so a ring finger longer than the index is common in both, and a ratio can't tell anyone a person's sex, which is why this page won't try. Wikipedia's review also notes that differences between ethnic groups have been reported as larger than the difference between the sexes, one more reason not to read much into your own figure.
The hormone idea, study by study
Manning's proposal was that the ratio is set before birth and reflects exposure to sex hormones. That would make it a marker you could read in an adult for something that happened in the womb. Many papers followed, linking it to all sorts of things. Here is what some direct looks at the hormone idea found.
| Paper | What they looked at | What they found | What it means for you |
|---|---|---|---|
| Manning et al., 1998 | The ratio, and hormones and sperm count in a clinic sample | Means of 0.98 and 1.00, plus correlations with hormones in that sample | The starting point. A proposal, from a clinic sample |
| Honekopp et al., 2007 | New data and a review of adult hormone studies | "In the normal population, 2D:4D and Dr-l are not associated with adult sex hormone levels" | Your ratio doesn't show your testosterone now |
| Honekopp and Watson, 2010 | A meta-analysis of the sex difference | Moderate, larger on the right hand, varying between studies | The average gap is real enough, and it's an average |
| Hollier et al., 2015 | Adult ratio against hormones in umbilical cord blood, in one cohort | The title says it: "not related" | One direct look at hormones at birth, and no link |
| Lolli et al., 2017 | How the two finger lengths scale, in 416 people | "2D does not vary in direct proportion to 4D", so the plain ratio is unsuitable for comparing groups, and it can build in an artefact of hand size | The number itself may be a flawed way to compare anyone |
| Richards, 2017 | A reply to Manning and Fink on prenatal hormones | The literature leans one way, yet "the link remains tenuous, with most reported effects not being statistically significant". Manning and Fink disagree, and cite significant results in males | Still argued over by the people who study it |
That last row is the fair summary. This isn't a debunked idea or a proven one. It is a proposed marker, with serious researchers on both sides, and several direct tests have come up empty. Results that do exist describe average tendencies across many people. Is palm reading real looks at why results like these so easily turn into stories about individuals.
What you can't conclude
Nothing about you as a person. Articles on this subject tend to jump from a group average to a personal verdict, about testosterone, looks, sex, sporting talent or money. No study here supports reading those off one person's fingers, and we won't say what yours means for any of them.
If something about your hormones, your health or your fertility is worrying you, a doctor can run real tests. A finger can't do that.
What palmistry says about the same fingers
Palmistry got to these fingers long before the hormone studies, for quite different reasons. Cheiro called the index "the finger of Ambition", and he wrote that first and third fingers "of equal length" were "the best sign of an equally balanced mind". He even advised employers on what a long first finger meant. Old books say these things with no data at all, so we pass them on as what they are. The work chapter of the Complete Palm Reading treats them as tradition, and says nothing about your hormones.
The palm reading guide shows where fingers fit in a reading of the whole hand, and hand types uses a different finger measure, your middle finger against your palm. For how our camera arrives at its figure, and what else it measures, see the methodology page and the other tools.
Read next
Sources
- The ratio of 2nd to 4th digit length
- Meta-analysis of digit ratio 2D:4D shows greater sex difference in the right hand
- 2D:4D and adult sex hormone levels: new data and a meta-analytic review
- Adult digit ratio (2D:4D) is not related to umbilical cord androgen or estrogen concentrations
- Digit ratio (2D:4D) and prenatal/perinatal sex hormones: a response to Manning and Fink (2017)
- A comprehensive allometric analysis of 2nd digit length to 4th digit length in humans
- Digit ratio
- Palmistry for All
- What You Should Know About Palmistry
- Hand landmarks detection guide