Did you know arm span ( or reach ) is approximately equal to height?

How to calculate arm span

We tested this out against a wall using chalk to mark reach and then standing next to the wall to see if it matched height. You should measure from finger tip to finger tip and not have a flat hand as in this photo.

We found my 6 year old’s arm span did equal his height and my 4 year old was a little taller than hers.

Ape index is the ratio of arm span relative to their height. So my little boy had an ape index of 1.

A arm span greater than height is thought to be advantageous in some sports such as swimming, as longer arms may give greater propulsion. A shorter arm span is useful for weight lifters as they don’t have to lift the weight as high.

Can you work out your Ape Index?

More human body science ideas

Can you work out how many feet tall you are too?

Or try some of these great preschool science ideas.

1. Emma

My little ones love this too! Great fun. I didn’t know it had a proper name though! (And apparently your foot is the length of your forearm too.)

1. ScienceSparks

I keep meaning to try that one!

2. rscionka

My fore arm is 3 inches longer than my foot and my arm span is 5 inches greater than my height… ape arms…

2. HELEN

interesting stuff! I will be checking out our ape index…I suspect that the males of the family have longer arm spans than height….good for reaching glasses from the top shelves!

1. ScienceSparks

Ha ha, good point!

3. Jodi

This is so simple but a really fun idea. Thanks for the inspiration.

4. Heather twinkl

Did not know that! Am now going to spend the next hour with my boys on this!

5. Itchy

I herd this along time ago on Braniac I think so have added their URL! but when I checked it my Span of my Arm’s is 2-3 inches LONGER than my Height so Wife laughed and said that I am an Ape!

6. Maria

If your arm length is significantly longer than you are tall it could be d genetic disorder called Marfan syndrome.

7. John Lukeward

I have an arm span of 76″ my height is 65″ a difference of nearly a foot. Is my arm span too long?