How to Calculate Area of a Sphere

Like a circle, a sphere has a radius and a diameter. However, because a sphere is 3-dimensional, it also contains volume and surface area, both of which are related to the 2-dimensional measurements. To calculate the surface area, use the formula 4 times Pi times the radius raised to the second power.

Things You'll Need

• Calculator

Instructions

1. Calculate the radius of the sphere. If you do not know the radius, the easiest way to calculate it is by first measuring the sphere around the widest part to get the circumference. Divide the circumference by Pi (3.14), and then by 2. For example, a sphere with a circumference of 20, divided by Pi, produces a diameter of 6.36. Dividing this by 2 produces a radius of 3.18.

2. Raise the radius to the second power by multiplying it with itself. In this case, 3.18 raised to the second power is 10.11.

3. Multiply this number by Pi. This example produces 31.75.

4. Multiply this result by 4. This example produces 127. Thus, a sphere with a radius of 3.18 inches has a surface area of 127 square inches, rounded down.

References

• Surface Area Formulas
• Surface Area Calculator