What this calculator does
Ape index compares arm span to height. It is reported either as a difference, wingspan minus height in centimetres, or as a ratio, wingspan divided by height. A 178 cm span on a 175 cm frame is +3 cm, or a ratio of 1.017.
It matters most in climbing, where reach between holds is a real constraint and a positive index genuinely helps. Most people sit within a few centimetres either way, and a span exactly equal to height, giving a ratio of 1.000, is close to the population average.
The formula
The difference is wingspan minus height, and the ratio is wingspan divided by height. Both describe the same thing, with the difference easier to picture and the ratio easier to compare between people of different sizes. Wingspan is measured fingertip to fingertip with arms held horizontally.
| Term | Meaning |
|---|---|
| Wingspan | Fingertip to fingertip with arms outstretched horizontally, also called arm span. |
| Positive ape index | Wingspan greater than height, generally an advantage in climbing and some combat sports. |
| Ratio form | Wingspan divided by height, around 1.0 for most people. |
| Reach | How far you can extend, which depends on shoulder mobility and torso length as well as arm length. |
The inputs explained
| Field | What to enter |
|---|---|
| Wingspan (fingertip to fingertip, arms out) (cm) | Wingspan in centimetres, fingertip to fingertip with arms horizontal. Easiest measured against a wall with help. |
| Height (cm) | Height in centimetres, without shoes. |
When to use it
Climbing
Reach between holds is a genuine constraint, and a positive index means some moves are static that would otherwise be dynamic.
Combat sports
Reach advantage is a standard consideration in boxing and mixed martial arts, where fight statistics list it alongside height and weight.
Equipment fitting
Rowing, swimming and cycling fit all depend on limb proportions rather than height alone, and the index is a quick summary of one of them.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
What does each wingspan give?
A fixed height of 175 cm across a range of wingspans.
| Wingspan | Ape index (difference) | Ape index (ratio) | Reading |
|---|---|---|---|
| 170 cm | -5.0 cm | 0.971 | Negative: wingspan shorter than height |
| 175 cm | +0.0 cm | 1.000 | Neutral: wingspan close to height |
| 180 cm | +5.0 cm | 1.029 | Positive: wingspan longer than height |
| 190 cm | +15.0 cm | 1.086 | Positive: wingspan longer than height |
Questions
What is a good ape index?
For climbing, positive helps, and +5 to +10 cm is a noticeable advantage. Most people fall between −5 and +5. It is one factor among many, and technique, finger strength and body composition matter considerably more than reach for most climbers.
How do I measure wingspan?
Stand with your back against a wall, arms outstretched horizontally at shoulder height, and have someone mark each fingertip. Measure between the marks. Doing it alone is difficult and tends to undermeasure, since it is hard to keep both arms fully extended.
Which form should I use, difference or ratio?
The difference is easier to picture and is what climbers usually quote. The ratio is better for comparing people of different heights, since +5 cm means proportionally more on a short frame than a tall one. Both are shown because both conventions are in use.
Does ape index change?
Not in adults, since it reflects skeletal proportions. It changes through growth in children and adolescents, where arms and legs grow at different rates from the torso, so a measurement taken during a growth spurt will not hold.
For vertical reach in basketball terms, see the dunk calculator. For strength relative to body size, see the Wilks score calculator.