I'm trying to worldbuild and one of my creatures is a 3 foot tall humanoid and I have no idea what they should weigh.
Does anyone know how much they would weigh or a math equation I could use to figure it out?
Thanks in advance
Worldbuilding Stack Exchange is a question and answer site for writers/artists using science, geography and culture to construct imaginary worlds and settings. It only takes a minute to sign up.Sign up to join this community
Assuming the same proportions as a "normal" human (bad assumption, see below), weight is proportional to volume, hence to the cube of height -- that is, a creature with double the linear dimension (height) would weigh 2^3 = 8 times as much, so your three foot dwarf would weigh about one eighth what a six foot human would.
However, notice the size of a mouse's legs relative to its body, vs. the size of an elephant's. Strength of limbs scales only as the square of height (it's based on cross sectional area rather than volume), so the larger the creature, the relatively thicker its limbs need to be in comparison to its height.
There are three ways a race evolved (or created) to be half as tall might deal with this: they might weigh more, by carrying additional muscle, making them stronger relative to their size and weight than the prototypical 6 foot human (or by running strongly to fat, perhaps as a store against famine or hibernation); they might have skinnier legs (and likely arms) relative to their height, breaking their proportions and making them more similar to a monkey or small ape in terms of body appearance; or (if created rather than evolved) they might maintain human proportions and simply have stronger legs relative to the rest of their body (the difference likely wouldn't make them incredible jumpers, but they might do well at power lifting).
Here is Commodore Nutt
He was an American entertainer and showman and a contemporary of General Tom Thumb.
Nutt was 29 inches tall and 25 pounds. General Tom Thumb was 40 inches (1 metre) and 70 pounds (32 kg).
I was a little skeptical of the 25 pounds for Commodore Nutt. But Google gave me this
from The Normal Higher Arithmetic an 1877 math textbook. Dang, Google!
So there is a fair range of weights for humans around your desired height.
Suppose they are similar to humans living in an earth-like environment.
BMI = mass (kg)/ height2 (m) = 703 × mass (lbs)/ height2 (in)
As told here:
Healthy BMI range is 18.5 kg/m2 - 25 kg/m2.
Therefore, healthy range of weight for a 3 feet tall person is 34.1 lbs - 46.1 lbs.