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.
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.