What you're going to possibly need:

- A Sphere
- Distance measuring tool (ruler, caliper)
- Calculator/Pen+Paper
- Graduated cylinder + water
- A brain (you're on Instructables.com - you've already got this...I'm not going to stress common sense all that much)

**Signing Up**

## Step 1: The Volume Formula

^{3 }

where:

- 4/3 is a constant
- Pi is a constant that for our purposes will = 3.14
- r is the radius of the sphere, which is the distance from the center of the sphere to any point on that sphere's surface

## Step 2: Gathering Information

**radius**of the sphere. There are several ways we can find the radius of a sphere. The more practical ways include deriving the radius from the diameter or the circumference.

You already know this, but:

- Diameter - the longest segment that can exist within the sphere; this is 2*the radius
- Circumference - the length of a circle projected by the sphere; this is 2*pi* the radius

**diameter**of the sphere by holding a ruler against the longest part of the sphere. Match up the beginning of the ruler with your right eye closed; then take the measurement with your left eye closed. This gives you a terrible approximation, but an approximation nonetheless. After finding the diameter, simply divide it by 2 to yield the radius.

You can find the circumference most easily by taking a string or a wire and wrapping it across the longest portion of the sphere. Then measure the length of the string. After finding the circumference, divide by 2*pi to yield the radius.

There is also a method to do this with gas, but I did not include it in my "Volume of a sphere." Otherwise, yours is pretty good, from my standpoint.

You can check mine out, here.