Ape Index Calculator
Enter your wingspan and height to get your ape index two ways — the ratio (wingspan ÷ height) and the difference (wingspan − height) — plus an estimated percentile against measured population data and what the number means for climbing, swimming, basketball and more. Everything runs in your browser; nothing is uploaded.
Calculate your ape index
Ratio method: ape index = wingspan ÷ height (neutral = 1.0, unit-free). Difference method: ape index = wingspan − height (neutral = 0, in your unit) — the convention climbers usually quote.
How to read your result
A positive ape index (ratio above 1.0, difference above 0) means your arms are longer than you are tall. Negative means the opposite; neutral is the Vitruvian proportion — arm span equal to height — that Leonardo da Vinci drew. The bands below are rules of thumb from climbing culture, not medical cutoffs:
| Ratio | Band | What it means |
|---|---|---|
| ≥ 1.06 | Very long reach | Top few percent of the population; typical of elite swimmers and NBA players. |
| 1.03 – 1.06 | Notably positive | Clearly above-average reach; often reported among elite climbers. |
| 1.005 – 1.03 | Slightly positive | A touch more reach than height; roughly the 32nd–76th percentile for men. |
| 0.995 – 1.005 | Neutral (Vitruvian) | Wingspan about equal to height — the most common zone. |
| 0.97 – 0.995 | Slightly negative | A touch less reach than height; completely normal. |
| < 0.97 | Notably negative | Wingspan clearly shorter than height; many strong athletes live here too. |
The percentile comes from a normal model of the arm-span-to-height ratio using the adult European reference: mean ≈ 1.015 for men and ≈ 1.008 for women, SD ≈ 0.021 (Gerver et al. 2020, Hormone Research in Paediatrics, adult values per Quanjer et al.). It is a rough estimate — distributions shift with age and population.
Worked examples
Example 1 — metric (ratio + difference)
Wingspan 180 cm, height 175 cm.
Step 1 — ratio: 180 ÷ 175 = 1.0286 → positive (above 1.0).
Step 2 — difference: 180 − 175 = +5 cm → positive (above 0).
Step 3 — percentile (men): z = (1.0286 − 1.015) ÷ 0.021 ≈ 0.65 → ≈ 74th percentile, band “slightly positive”.
Example 2 — imperial (same person, different unit)
Wingspan 72 in, height 70 in.
Step 1 — ratio: 72 ÷ 70 = 1.0286 → identical to Example 1, because the ratio is unit-free.
Step 2 — difference: 72 − 70 = +2 in → the number changes with the unit, the proportion does not.
That is why the ratio is better for comparing people and the difference is better for a quick intuitive quote.
Example 3 — Michael Phelps (widely reported measurements)
Wingspan 203 cm, height 193 cm.
Step 1 — ratio: 203 ÷ 193 = 1.0518 → 1.05.
Step 2 — difference: 203 − 193 = +10 cm (+3.9 in).
Step 3 — percentile (men): z = (1.0518 − 1.015) ÷ 0.021 ≈ 1.75 → ≈ 96th percentile, band “notably positive”.
What counts as “good” — by sport
| Sport | Why reach matters | Benchmark |
|---|---|---|
| Rock climbing / bouldering | Longer reach can span bigger moves and skip holds. | Positive helps, but evidence is weak — see “What the science says”. |
| Swimming | Longer arms can produce a longer, more efficient stroke. | Phelps ≈ 1.05 (+10 cm). |
| Basketball | Reach helps defense, rebounding, and shooting over defenders. | NBA average 1.063 (Epstein, The Sports Gene). |
| Boxing / combat | A positive index usually means longer punching reach. | Reach advantage grows with the difference in cm/in. |
| Football (goalkeeper) | A higher index can compensate for being shorter than the pro norm. | Noted in shorter elite keepers (Wikipedia). |
Measured benchmarks
| Who | Wingspan | Height | Ape index | Source |
|---|---|---|---|---|
| Michael Phelps (swimming) | 203 cm | 193 cm | 1.05 (+10 cm) | Wikipedia “Ape index” |
| Average NBA player | — | — | 1.063 | David Epstein, The Sports Gene |
| Desmond Bane (NBA) | 193 cm | 196 cm | 0.985 (−3 cm) | Wikipedia “Ape index” |
| Adult European avg (men) | — | — | ≈ 1.015 | Gerver et al. 2020 / Quanjer et al. |
| Adult European avg (women) | — | — | ≈ 1.008 | Gerver et al. 2020 / Quanjer et al. |
Athlete figures are widely reported values; population averages are measured reference data (see sources below).
How to measure your wingspan correctly
- Use a wall. Stand with your back flat against it, heels together.
- Arms out. Stretch both arms straight out to the sides at shoulder height, palms facing forward, fingers together and fully extended. Do not shrug your shoulders up.
- Mark both ends. Have someone mark the wall at the tip of each middle finger — or mark one side, then carefully mark the other without moving.
- Measure straight. Measure the distance between the two marks in a straight line.
- Measure height barefoot, standing tall, heels together, looking straight ahead. Use the same unit for both, and measure at the same time of day (spine compression changes height slightly).
- Measure twice. If the two readings differ by more than ~1 cm (½ in), take a third and average.
What the science actually says
Climbing culture treats ape index as a big deal; the research is more modest:
- Lattice Training (2026) analysed thousands of climber records and found ape index has only a weak relationship with climbing grade — “real enough to be statistically detectable, but small.” Finger strength and training matter far more.
- Watts et al. (2003) studied young competitive rock climbers and found no correlation between ape index and climbing ability (possibly because competitive climbers already self-select for reach).
- Ozimek et al. (2017), in the Journal of Strength and Conditioning Research, found elite Polish boulderers differed from controls in arm span as a group — but ape index was not a significant predictor of performance differences between elite and non-elite athletes.
- Moss et al. (2001) found ape index was one of several variables with diagnostic value when comparing male and female competition climbers.
- Gerver et al. (2020) published reference charts for arm-span-to-height ratio (2,595 children, plus adult European data from Quanjer et al. covering 13,947 subjects) — the source of this calculator's percentile model.
Bottom line: a positive ape index is a small, real advantage in reach sports — not a destiny. Technique, strength, and training dominate.
Not to be confused with ABSI
Ape index (this page) is wingspan ÷ height — a sports metric about reach. ABSI (A Body Shape Index, Krakauer & Krakauer 2012) is waist ÷ (BMI2/3 × height1/2) — a medical research metric about body shape. Same word “index”, completely different formula and purpose. If you meant the health metric, see our ABSI calculator.
Frequently asked questions
What is ape index?
Ape index (also called ape factor or gorilla index) is the ratio of your arm span (wingspan, fingertip to fingertip) to your height. It is usually computed as wingspan ÷ height, where 1.0 is neutral (arms exactly as long as you are tall), above 1.0 is a positive ape index, and below 1.0 is negative. Rock climbers also use the difference form: wingspan − height, where 0 is neutral. The term was coined by Frisbee throwers at UC Berkeley in 1975.
How do I calculate my ape index?
Use either of two methods. Ratio method: divide your wingspan by your height — for example, a 72-inch wingspan and 70-inch height gives 72 ÷ 70 = 1.029. Difference method: subtract your height from your wingspan — 72 − 70 = +2 inches. Both describe the same proportions; the ratio is unit-free (the same in cm or inches) while the difference keeps the unit you measured in.
What does a +2 ape index mean?
A +2 ape index uses the difference method: your wingspan is 2 units longer than your height (2 inches or 2 cm, depending on what you measured in). For a 70-inch-tall person, that means a 72-inch wingspan, which is about a 1.029 ratio. It is a modest positive ape index — slightly above average, common among athletes in reach sports.
What does an ape index of 1.05 mean?
An ape index of 1.05 means your wingspan is 5% longer than your height. For someone 180 cm tall, that is a 189 cm wingspan (+9 cm). It is a clearly positive ape index — roughly the 95th percentile for adult men against the European reference data — and is in the range often reported for elite swimmers and basketball players.
What is a good ape index for climbing?
A positive ape index (above 1.0) is traditionally considered helpful in climbing because longer reach lets you span bigger moves. But the science is humbling: a 2026 Lattice Training analysis of thousands of climbers found ape index barely predicts climbing grade, Watts et al. (2003) found no correlation in young competitive climbers, and Ozimek et al. (2017) found it was not a significant predictor of performance differences between elite and non-elite climbers. Finger strength, technique, and training history matter far more.
Can I change or train my ape index?
No. Your ape index is set by your bone structure and does not change meaningfully after skeletal maturity — you cannot train your arms longer. Some climbers have claimed exercise can improve the ratio, but that view is controversial and not supported by evidence. What you can train is functional reach: shoulder mobility, hip flexibility, and movement technique all make your existing wingspan go further.
What is the average ape index?
The textbook average is 1.0 — the Vitruvian proportion where arm span equals height. Measured population data refine this: in the European adult reference (Quanjer et al., summarised in Gerver et al. 2020), the average arm-span-to-height ratio is about 1.01–1.025 in men and 1.005–1.02 in women, rising slightly with age. The calculator's percentile uses these reference values, so 50th percentile sits near 1.01 rather than exactly 1.0.
Which method should I use: ratio or difference?
Use the ratio (wingspan ÷ height) when comparing people of different heights — it is scale-invariant, so a 1.60 m climber and a 1.90 m climber with the same ratio have identical proportions. Use the difference (wingspan − height) when you want an intuitive number in your own unit, which is the convention in climbing culture (e.g. '+5 cm'). This calculator shows both, so you never have to choose.
Do professional athletes have high ape indexes?
Often, but not always. Swimmer Michael Phelps has a widely reported 203 cm wingspan at 193 cm tall — an ape index of about 1.05. The average NBA player sits at 1.063 (per David Epstein's The Sports Gene), while NBA guard Desmond Bane plays at a high level with a 0.985 ape index, nicknamed 'T-Rex'. Reach helps in specific sports; it is not a requirement for elite performance.
Is ape index important in sports other than climbing?
Yes, wherever reach matters. In swimming, longer arms can mean a longer, more efficient stroke (Phelps: 1.05). In basketball, reach helps defense, rebounding, and shooting over defenders — the NBA average is 1.063. In boxing, a positive ape index usually means longer reach for the jab. In football, a higher index can compensate for a goalkeeper who is shorter than the professional norm.
How do I measure my wingspan correctly?
Stand with your back flat against a wall, feet together, and stretch both arms straight out to the sides at shoulder height, palms facing forward, fingers together and extended. Have someone mark the wall at the tip of each middle finger, then measure straight between the marks. Keep your shoulders down (do not shrug), measure twice, and use the same unit for height — measured barefoot, standing tall, at the same time of day.
What is the difference between ape index and ABSI?
They share the word 'index' and nothing else. Ape index is wingspan ÷ height — a sports and climbing metric about reach. ABSI (A Body Shape Index, Krakauer & Krakauer 2012) is waist circumference ÷ (BMI^(2/3) × height^(1/2)) — a medical research metric about body shape and mortality risk. Do not confuse the two: this page is about reach, not health.
Sources
- Wikipedia — “Ape index” (formula, Vitruvius, term coined 1975 by UC Berkeley Frisbee throwers, Phelps 1.052, NBA 1.063, Bane 0.985).
- Gerver, W.J.M. et al. (2020). “Arm Span and Its Relation to Height in a 2- to 17-Year-Old Reference Population.” Hormone Research in Paediatrics 93:164–172. DOI 10.1159/000508500 — reference table for AS/H (ratio), adult European values per Quanjer et al.
- Quanjer, P.H. et al. — multi-ethnic arm-span reference (13,947 subjects aged 5–99), via Gerver et al. 2020.
- Lattice Training (2026). “Does Ape Index Matter in Climbing?” — weak correlation with grade across thousands of records.
- Watts, P.B. et al. (2003) — no correlation between ape index and ability in young competitive climbers.
- Ozimek, M. et al. (2017). Journal of Strength and Conditioning Research — elite Polish boulderers vs controls.
- Moss et al. (2001) — ape index among diagnostic variables in competition climbers.
- David Epstein — The Sports Gene, “The Vitruvian NBA Player” (NBA average 1.063).
- Measurement method summarised from standard anthropometric practice (cf. procalculator.co.uk, mrclimb.com).
Related tools: Archery Draw Length Calculator (also starts from your wingspan) · Dunk Calculator (reach + vertical jump).
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