The surface area to volume ratio is a way of expressing the relationship between these parameters as an organisms size changes. The surface-area-to-volume ratio also called the surface-to-volume ratio and variously denoted savol or SAV is the amount of surface area per unit volume of an object or collection of objects. Essentially it is area of an object that is exposed to the external environment surface area compared to the amount within an object volume.
Small or thin objects have a large surface area compared to the volume.
For a sphere surface area is S 4PiRR where R is the radius of the sphere and Pi is 31415. For the sphere the volume is 43 pi r 3. Surface area of the sphere will be covered completely fill the region of four circles all of the same radius as of the sphere. Plants also need carbon dioxide for photosynthesis.