# Q & A: elephant weight

Q:
How many pounds do elephants weigh?
- Octavia (age 17)
Sallis,Mississippi, United States
A:
I love this question!

First of all, like humans, not all elephants weigh the same.  But one can make a guess for the average weight of an elephant.  Or you can go out and weigh a particular elephant.  How would you  do that?  Put the elephant onto a boat. Measure the displacement by looking at the water-line, and record this mark. Remove the elephant. Add known weights to the boat (i.e 1kg weights) until the water level reaches that of the elephant. Then, count and calculate the weights. This should be the exact weight of the elephant!

If you want to make an educated guess of the weight of an elephant you need to make a model of the elephant and plug in some numbers.  As the apocryphal physicist replied when asked to describe a cow he said,  "consider a sphere...".   Actually a cylinder is a better starting point for an elephant.   Let's make a model of an elephant:  a cylinder supported on four massles legs.  The weight of this model is W = rho*pi*R^2*L where rho is the density of elephant flesh, aproximately 1000 Kg/m^3,  R is the radius of the cylinder and L is the length of the cylinder.  I browsed through  some Google  images of elephants with people standing nearby and came up with some estimates:  R =  0.4 meters, L = 3 meters.  The model answer is 4.6 tons. (That's 9200 pounds.)

I then Googled "weight elephant" and came up with answers varying from 4 to 6 tons.