Ape index, also called the gorilla index, compares your arm span to your height. The common version subtracts height from arm span, so a person 178 cm tall with a 183 cm span has an ape index of plus 5 cm. Another version divides arm span by height to give a ratio instead.

Is a positive ape index good for climbing?

Yes, a positive ape index means your reach is longer than your height, which lets you span between holds that are farther apart. It is often an advantage in rock climbing and bouldering, though technique, strength and flexibility usually matter more than reach alone.

How do I measure my arm span?

Stand with your back to a wall and stretch both arms out sideways at shoulder height, making a T. Measure the straight line distance from the tip of one middle finger to the tip of the other. Measure your height without shoes, then subtract height from span to get your ape index.

Ape Index Calculator

This ape index calculator compares your arm span to your height, the measurement climbers use to describe reach. The ape index, sometimes called the gorilla index, is most often given as your arm span minus your height: a positive number means your reach is longer than you are tall, a negative number means the opposite, and zero means your span and height match, the so called Vitruvian build. You enter your height and your arm span, both in centimetres, and the calculator returns your ape index in centimetres along with the arm span to height ratio, which is simply your span divided by your height. A ratio above 1 confirms a positive ape index. Rock climbers and boulderers pay attention to this because a longer reach lets you bridge holds that are spaced farther apart, so a positive ape index is generally treated as an advantage, though good footwork, finger strength and flexibility usually count for far more than reach alone. Swimmers and boxers track it too. To measure your arm span, stand with your back flat to a wall, stretch both arms out sideways at shoulder height to form a T, and measure fingertip to fingertip, then measure your height without shoes. Enter both figures below to see where you sit.

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Height

Arm span

+5 cm

your ape index (arm span minus height)

Span to height ratio1.03

Arm span183 cm

Height178 cm

A positive ape index of +5 cm means your reach is longer than your height, generally an advantage in climbing and reach sports.

Ape index is a body measurement, not a fitness score. Reach helps in climbing, but technique and strength usually matter more. Measure without shoes for the fairest comparison.

How it works

The ape index is your arm span minus your height, both measured in the same units. A result above zero means your arms reach farther than your standing height, below zero means shorter. The span to height ratio expresses the same relationship as arm span divided by height, so a ratio above 1 lines up with a positive ape index and a ratio below 1 with a negative one. Most people sit within a few centimetres of zero, with a ratio close to 1.

Worked example

Say you are 178 cm tall with an arm span of 183 cm. Your ape index is 183 minus 178, which is plus 5 cm, so your reach is 5 cm longer than your height. The ratio is 183 divided by 178, about 1.03. That positive ape index is the kind of reach advantage climbers look for when spanning between distant holds.

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