how do you find this?
 

how do you find the how many square inches your body is?

Um, you don't. Finding the exact area of a complex solid is pretty much impossible.

Just do some fermi stuff.

You could get someone to kill you, cut your body into little chunks, blend it up bit by bit, and use one of those thingies to measure how much body goo there is. But I guess by then you wouldn't really care.

Couldn't you also submerge yourself in water and measure how many cubic inches of water is displaced?

Wouldn't that be a measure of volume, and not surfcae area?

It's not surface area he's looking for, anyway..

Yes, it would.

well it has to do with something with skin because our teacher told us our skin takes up like 21 square inches or something of our body

Make sure you are asking the right question. Do you simply want the surface area (Like MJ stated, and as you said, "square inches"), or do you want the volume of your body (Cubed inches)?

Well, you can estimate it by dividing your body into sections and estimating their individual surface areas, but you wouldn't get acuracy past maybe two significant digits, and I'm pretty sure that there are at least 4 digits in the surface area of the human body in square inches.

Look up the Mosteller formula.