Pretending that the earth and its atmosphere are perfectly spherical and not elliptical, we can calculate the approximate volume of the stratosphere. The radius of the Earth is roughly 6,378.1 km. The troposphere, which lies below the stratosphere is around 18 km at its highest height. The stratosphere extends to around 42 km above the troposphere. Finding the difference between the volume of the earth including the atmosphere and the earth up to the troposphere gives the approximate volume of the stratosphere. It is approximately 22 thousand million kiloliters.