You may have noticed a problem with your question if you tried to measure the length and width of a sphere. You are missing the 3rd dimension and still you will not get the right answer.
The formula to measure the surface area of a sphere is:
pi * diameter^2 (or 4 * pi * radius^2)
EDIT: U R 2 oblivious -- Volume is calculated with:
(pi * diameter^3) / 6 (or 4/3 * pi * radius^3)
The earth is not a perfect sphere (bit flattened at the poles) but close enough for this. The radius of the earth is 6.37 x 10^6 meters. If you do the math you get:
1,097,509,500,000,000,000,000 cubic meters (or 1.09 sextillion cubic meters). Quite a lot and the earth is not even all that big for a planet!
The exact answer after fiddling with exact measurements for a not quite spherical earth is 1,083,206,246,123,080,894,852 cubic meters.