How to Determine Surface Area to Volume Ratio

In biology, the surface to volume ratio is an important concept. As the size of an organism increases, the volume increases faster than the surface area. This is why small organisms often have high metabolic rates, as they have more surface area proportionally to lose heat, and thus need more energy relative to larger organisms. Calculating the ratio between the surface areas and volumes of different objects is a common exercise in biology classes to help illustrate this concept. Differently shaped objects use different formulas; cubes and spheres are commonly used in classes.

Things You'll Need

• Pencil
• Paper
• Calculator

Show More

Instructions

1. • 1

     Calculate the surface area. For a cube, this is the length of one side of the cube squared times six. For a sphere, this is the radius of the sphere squared times pi (a constant number) times four.

   • 2

     Calculate the volume. For a cube, this is the length of one side of the cube cubed, or to the third power. For a sphere, this is the radius of the sphere cubed times pi times four, then divided by three.

   • 3

     Divide the total surface area by the volume to get the surface area to volume ratio.