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Ape Index Calculator: Should You Even Care About It? (2024)

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Ape Index Calculator

Note: it may take a few seconds for the calculator to appear below

The climbing world has always been interested in the Ape Index for some reason. As if this untrainable factor could make or break a climber’s career.

In this article, we’ll go over the findings from scientific research studies to determine how important the Ape Index actually is. From there, we’ll look into the ape indices of the most famous rock climbers to see if there’s a positive correlation between elite performance and a high ape index.

What’s the Ape Index?

The Ape Index measures how your wing span compares to your height. It can be expressed as a ratio (e.g., 1.05) or as a difference (e.g., +7 in/18 cm).

Interestingly, it’s a concept dating back to Roman times: Vitruvius, an architect, engineer, and writer, argued in 15 BC that a “well-made man” has an arm span equal to his height. Later, Leonardo da Vinci illustrated the concept with his famous Vitruvian man drawing (1492).

Vitruvian man Leonardo da Vinci

Of course, neither Vitruvius nor da Vinci named this “discovery” the ape index. That we owe to climbing slang, it seems.

Note: in this article, we’ll use the term ape index, but some people also refer to it as “gorilla index” or “ape factor.”

Does the Ape Index Matter?

The Ape Index has fascinated generations of athletes because of its potential ability to predict sports performance. Having a large wingspan has obvious potential benefits:

  • Longer body surface to propel yourself in the water as a swimmer
  • More reach as a boxer to hit your opponent
  • Better ability to block and score shots as a basketball player
  • And, of course, more reach to grab holds as a climber!

However, is that really the case?

Climbing index relation to performance

What does science say?

That’s where things get murky. A study by Mermier et al. (2000) (1) published in the highly reputed British Journal of Sports Medicine measured the performance of 44 climbers on different routes. Their goal was to determine what variables influenced climbing performance. The researchers identified three main groups:

  • Training (e.g., years of climbing, weekly training hours)
  • Anthropometric (e.g., height, weight, arm span)
  • Flexibility (e.g., shoulder and hip flexibility)

After performing a multiple regression analysis, they concluded that the training part explained 59% of the total variance in climbing performance. On the other hand, anthropometric and flexibility variables only explained 0.3% and 1.8%, respectively.

bouldering climber sending indoor route

Similarly, a study by Watts et al. (2003) (2) investigating the anthropometric characteristics of young competitive rock climbers (also published in the BMJ) concluded that there was “no correlation between the ape index and climbing ability.” However, they suggested these results may be due to the low variability in the ape factor among the climbers in the study. In other words, the higher-than-average ape index of these young climbing rockstars may be exactly what led them to practice sport climbing competitively in the first place!

More recently, Ozimek et al. (2017) (3) also failed to identify the Ape factor as a significant predictor of performance differences when comparing elite and non-elite athletes in climbing.

The only study we found supporting the beneficial impact of higher ape indexes on climbing efficiency is the one by Moss et al. (2001) (4). It concluded that male climbers placed higher than their female counterparts in competitions. However, the researchers couldn’t measure the influence of each factor. They concluded that “this may be explained by the higher body fat percentage, and lower grip strength, height, ape index, and power output of the female climbers.”

In other sports

michael phelps ape index
Michael Phelps at the 2016 Rio Olympics. The swimming champion has a score of 1.03 or +2″ (5 cm).

As for climbing, science doesn’t support the positive effect of a higher ape index on swimming performance (5). Could the ape index be completely irrelevant after all?

Should you care about the Ape Index?

As we have seen with our scientific literature review above, it doesn’t seem that an ape index greater than 1 (ratio) gives a competitive advantage. Similarly, there’s nothing indicating that a lower ape index can negatively impact your ability.

However, let’s imagine for a second that the Ape index does matter. Meaning that having longer arms than your height could lead to better rock climbing ability. Similarly, shorter arms than height would be detrimental to performance.

Even if this was true, how would this help us to become better climbers?

The ape index is not among the trainable factors. It doesn’t matter if you stretch every day, even from a young age; your arm span and height are determined by genetics. There’s no way around it. If anything, you might lose a bit of height as you get older, but surely that’s not something any of us would welcome!

Athlete on overhang route with positive ape index (climber wingspan is higher than height)

However, the Ape factor could be a way to compare yourself apple to apple to other climbers. For example, if you’re stuck on a particular boulder problem, the beta may come from another climber with a similar ape index ratio. This leaves us with surveying climbers in the gym or the crag for their Ape index. In hindsight, not the most practical solution to conquer boulders and routes (maybe an app?).

Our advice: don’t worry about it. While having a positive ape index can boost confidence in one’s abilities to crush routes, it shouldn’t discourage climbers with a negative ape index. And, above all, it shouldn’t deter prospective climbers from trying climbing!

For example, Alexander Megos, one of the most accomplished climbers, has an index of 1. It certainly doesn’t prevent him from on-sighting 9a (5.14d) routes!

Famous Climbers’ Ape Indices

ClimberHeightArm spanApe Index
Kai Lightner75 in (190.5 cm)82 in (208 cm)1.09
+7″ (17.5 cm)
Daniel Woods68 in (172.7 cm)72 in (182.9 cm)1.06
+4″ (10.2 cm)
Tomoa Narasaki66.9 in (170 cm)70.9 in (180 cm)1.06
+4″ (10 cm)
Shauna Coxsey64.2 in (163 cm)67.5 (171.5 cm)1.05
+3.3″ (8.5 cm)
Alex Honnold70.9 in (180 cm)74 in (188 cm)1.04
+3.1″ (8 cm)
Chris Sharma72 in (182.9 cm)74.5 in (189.2 cm)1.03
+2.5″ (6.3 cm)
Jonathan Siegrist65.5 in (166.4 cm)67 in (170.2 cm)1.02
+1.5″ (3.8 cm)
Brooke Raboutou62 in (157.5 cm)63 in (160 cm)1.01
+1″ (2.5 cm)
Adam Ondra73.2 in (186 cm)73.6 in (187 cm)1.01
+0.4″ (1 cm)
Lynn Hill62 in (157.5 cm)62 in (157.5 cm)1.00
Alexander Megos68.1 in (173 cm)68.1 in (173 cm)1.00
Lynn Hill bouldering
Lynn Hill.

How to measure your Ape Index?

There are two methods to calculate it. Not to worry, they are both very simple and use the same measurements.

What to measure

To calculate your ape index, you need your height and arm span.


The height is obvious. If you’re not sure, you can always ask your doctor on your next visit.


The wingspan (or arm span) is a bit more difficult as it’s not something we commonly measure. Here are the steps to measure your wingspan:

  • Stand against a wall with your arms abducted horizontally
  • Measure the greatest distance, from the tips of your extended fingers, between your right and left hands

Method 1: height to arm span ratio

Formula: height/arm span

Example: Adam Ondra is 73.2 in tall (186 cm) with a wingspan of 73.6 in (187 cm).

73.6/73.2 = 1.01

187/186 = 1.01

Method 2: arm span minus height

Formula: arm span – height

Example: Using Adam Ondra’s example again, we subtract 73.2 in (186 cm) to 73.6 in (187 cm).

73.6 – 73.2 = +0.4 in

187 – 186 cm = +1 cm

As we can see with the subtraction method, Adam Ondra’s ape index is just slightly positive; it’s certainly not exceptionally high! Considering his mind-blowing performances, this comfort the studies’ results we discussed above that concluded the ape index is not what makes a great climber.

To make the calculation easier, we created this calculator.

Boulderer reaching hold artificial rock wall


The Ape index is a popular topic among climbers, almost like folklore. While there’s a common belief that some of the best climbers have a high ape index, it’s not exactly true. Many of the world’s best climbers have a “standard” ape index.

Also, science hasn’t yet been able to prove the benefit of a higher ape index on performance, neither in climbing nor in any other sports.

So, let’s all forget about it and look for other excuses for our failed sends. The miracle solution to climbing harder is… to climb harder.

bouldering dyno move outdoor

Frequently Asked Questions (FAQs)

What is a normal ape index?

A normal ape index is 1 (ratio) or 0 (difference) if we refer to Vitruvius and Leonardo da Vinci. It means that the wingspan is equal to the height of the person. But who are they to tell?

Is a +5 ape index good?

Define good. A +5 ape index means that your arm span is longer than your height by 5 inches. That’s quite high compared to the average person. However, as we’ve seen in this article, while it may help with performance, there’s no reason to believe that it’s a requirement to become a high-level climber.

Is a positive ape index good?

It can help, but there’s only anecdotal evidence to suggest it positively impacts athletic performance. Studies show that training is the most important factor in becoming good at climbing.

How do you calculate ape?

Measure your height and wingspan. Divide wingspan by height to get your ape index ratio, or subtract height from wingspan to get the ape index as a difference value.

Who has the biggest ape index?

That may very well be Kai Lightner, who posted on Instagram on the topic (7). The 10-time Youth National Championship winner has a 6′ 10″ wingspan for a 6′ 3″ body height. That’s a 1.09 ape index ratio (or +7″).

What’s the sloth index?

The sloth index is a humorous index invented by Ryan Siacci of Outside/Climbing.com (8). “The sloth index is similar to the ape index but excludes the torso.” In the same article, Ryan lists many other folklore indexes. My favorite? The Beanie Index determines how hard you can boulder based on the number of beanies you own!


Physiological and anthropometric determinants of sport climbing performance
Mermier et al. (2000). British Journal of Sports Medicine.

Anthropometry of young competitive sport rock climbers
Watts et al. (2003). British Journal of Sports Medicine.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1751349/ (extract)
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1751349/pdf/v037p00420.pdf (full article)

The role of physique, strength and endurance in the achievements of elite climbers
Ozimek et al. (2017). PLoS One.

A comparison of male and female teenage sport rock climbers from a high school climbing league
Moss et al. (2001). Medicine & Science in Sports & Exercise.

Anthropometrics related to the performance of a sample of male swimmers
Perciavalle et al. (2014). Perceptual and Motor Skills.

YouTube: Adam Ondra #38: What is the best body type for climbing?
https://www.youtube.com/watch?v=yFfkOM8RgAU (retrieved on 10/19/2022)

Instagram: @kailightner. What’s my ape index?
https://www.instagram.com/p/BdsiOwAlPkB/?hl=en (retrieved on 10/19/2022)

Ryan Siacci’s Writer Page
https://www.climbing.com/byline/ryan-siacci/ (retrieved on 10/19/2022)

One Comment

  1. The 2001 study on female climbers couldn’t be further from the truth. The reason there’s more male climbers at the top is because there’s significantly more male athletes to begin with, at all levels. 1. Higher body fat percentage doesn’t limit female performance but rather helps it. Women are more efficient at converting glycogen to energy, meaning women are better at converting fat into fuel once the primary source of energy, glucose, drops. 2. Grip strength is relative to hand size. In relative terms, trained women have the same strength and it’s more than enough to support lighter female body. 3. The power output part isn’t even explained, but nothing limits for female athletes. Testosterone isn’t the only anabolic hormone that builds muscle, women have more HGH. 9 out of top 10 strongest pound for pound people are currently women (according to openpowerlifting), despite female powerlifters being a very small understudied minority. So nothing physiologically limit performance of female athletes, in fact climbing is one of the few sports that has a few women in the top 100 athletes, again, despite women being a minority in sports. Please stop spreading ignorance about female physiology in exercise science, it’s bad enough. Remember to factor in sociocultural factors

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