"Ape index" sounds like a joke measurement, but it is one of the oldest and simplest body proportions: how your arm span compares with your height. Climbers, swimmers and combat-sport fans talk about it constantly, and lifters argue about what it means for the deadlift and the bench press. This guide explains what the number is, how to measure it properly, what the typical range looks like, and what it does and does not tell you.
What ape index means
Your ape index is your arm span minus your height. Arm span is the distance from the tip of one middle finger to the tip of the other when your arms are stretched straight out to the sides. You will see it written two ways:
- As a difference: span minus height, such as +5 cm (+2 in) if your span is 5 cm longer than you are tall.
- As a ratio: span divided by height, such as 1.03.
The two say the same thing. A person who is 170 cm tall with a 175 cm span has an ape index of +5 cm, or a ratio of about 1.03. The ratio is handy because it works for any height, while the difference is easier to picture.
The word "ape" comes from the observation that apes have arms that are long relative to their bodies. In humans the term is simply shorthand for "arms longer than height", and many people with a positive ape index have never given it a thought. The same idea appears as wingspan in basketball and swimming and as reach in boxing and MMA.
What counts as a normal ape index
Most adults are close to "square", meaning their arm span is about equal to their height. A typical difference is within 2 to 3 cm (about an inch), in either direction.
| Ratio (span ÷ height) | What it means |
|---|---|
| Clearly below 1.00 | Arm span shorter than height (negative ape index) |
| About 1.00 to 1.02 | Roughly equal, the most common result |
| About 1.03 and above | Long reach (positive ape index) |
These bands are rough guides rather than medical cut-offs. An ape index of +1 or −1 cm is within normal measurement error, so do not read anything into it. Extremely long reaches do exist and are over-represented among elite swimmers and basketball players, partly because those sports select for them. Michael Phelps is the classic example: he is widely reported to stand around 6 ft 4 in with a wingspan of about 6 ft 7 in, a ratio of roughly 1.04.
How to measure your ape index accurately
A tape measure and a flat wall are enough. A helper makes it far more accurate.
- Measure your span. Stand with your back, shoulders and heels against a wall. Raise both arms straight out to the sides at shoulder height, palms facing forward, fingers extended. Have your helper mark the wall at the tip of each middle finger, or measure fingertip to fingertip with a tape held level. Do not stretch beyond a natural reach.
- Measure your height. Stand barefoot with your heels against the wall, look straight ahead and measure from the floor to the top of your head. Height changes by up to a centimetre or two across the day because the spine compresses, so measure at the same time of day each time.
- Repeat twice and use the average of the two readings.
- Do the sum. Subtract height from span, or divide span by height.
Measuring alone is the biggest source of error, because it is hard to hold your arms level and read the tape at the same moment. If you cannot get help, tape a long sheet of paper to the wall, press your fingertips to it and mark the ends yourself.
You can also get an arm-to-height ratio from a photo. The Body Proportions Calculator measures your arm ratio along with heads tall and leg-to-torso ratio from one front-facing photo, entirely in your browser. A tape-measure reading is still the more accurate of the two.
What a long ape index helps with
Arm length changes leverage, so it tends to help in some activities and hinder in others.
Where long arms tend to help
- Climbing. A longer reach lets you hold a hold that a shorter climber has to jump or reposition for. It is a real advantage on reachy routes, although finger strength, technique and footwork matter more.
- Swimming and rowing. A longer span can mean a longer pull through the water and a longer stroke.
- Boxing and MMA. Reach lets you strike from further away and makes you harder to hit. It is why reach is listed next to height in fight records.
- Basketball and volleyball. Wingspan helps with blocking, rebounding and contesting shots.
- Deadlift. Longer arms mean the bar starts closer to your hips and travels a shorter distance, which many lifters find a mechanical advantage.
Where long arms tend to hinder
- Bench press. A longer arm means a longer range of motion for the bar, so you do more work for the same weight. Lifters with long arms often prefer a wider grip or an arched setup to shorten the path.
- Push-ups and dips. The same range-of-motion effect applies.
- Pull-ups. You travel further to get your chin over the bar, although the extra reach helps you grab it.
Short arms tend to do the reverse: easier pressing, harder deadlifting off the floor. Remember that these are tendencies. Torso length, leg length, muscle insertions and technique all change the picture, and no one has ever been made or broken as a lifter by their ape index alone.
Can you change your ape index?
No. Both numbers are fixed by skeletal growth, which is mostly decided by genetics and finished by the late teens or early twenties. Stretching, hanging from a bar and "reach-increasing" routines do not lengthen your bones. The only things that change are the small differences caused by posture, time of day and measurement error.
What you can change is how you use the proportions you have. A long-armed lifter can choose bench and deadlift setups that suit their leverage, and a short-armed climber can train the dynamic moves that make up for a shorter reach.
Ape index, body proportions and attractiveness
Ape index is one of several proportion measurements used to describe a body, alongside leg-to-body ratio, heads tall and shoulder-to-waist ratio. The body proportions guide shows where each of them sits. Unlike shoulder-to-waist ratio, which you can influence through training and fat loss, ape index is a purely descriptive number. It says something about leverage, not about health or attractiveness, and we are not aware of reliable evidence that a particular ape index is more or less attractive. Treat it as a fun fact about your frame and a clue for choosing sports and lifting setups that suit you.
How to use your result
Measure it, note whether you are negative, neutral or positive, and leave it at that. If you climb or swim, a positive ape index is a small edge worth knowing about. If you lift, use it to pick setups that fit your leverage rather than copying someone with different proportions. If you are simply curious, enjoy being one of the many people with perfectly average proportions.
For the other numbers that describe your build, the Body Proportions Calculator gives you several from a single photo, and the Body Report combines all your measurements into one personal plan. Please also read our disclaimer.