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Step 1
**Get the height**
If you don't already know how tall (high), the cylinder is, then you'll need to measure it.
TIP for students: Be sure you use the proper ruler. For example, don't use a standard ruler with inches if you want your answer in metric. Use a metric ruler that has millimeters, centimeters, meters, etc. In public school, it's very common to use centimeters. -
Step 2
**Get your radius**
If you are given the diameter but not the radius, simply divide by 2. That's because diameter measures all the way across the top. Radius is 1/2 way. In other words, you start "dead center" and measure outward.
If you aren't given the radius or diameter, then you'll need to use a ruler to find it. The simpliest way is to measure the entire width across the top or bottom, and then divide by 2. In other words, find the diameter first. And then divide it by 2 to get your radius. -
Step 3
**Use this formula**
Volume = The radius squared x PI x height.
a) To get the radius squared, simply multiply the radius by itself. In other words, radius x radius.
TIP: A common mistake is to multiply the radius by 2. Watch for this error!
b) Then your answer from (a) and multiply it PI (3.14159....) however far out you need to go.
TIP: Some calculators have a button for PI that you can use. And it may or may not be adjustable as far as the number of decimal places it goes out. If not, then you'll simply adjust (round) at the final step (c).
c) Multiply your answer from (b) by your height. This will give you the volume. If necessary, round your answer accordingly.
The end result will be your volume. And your unit of measure will be cubic______. In other words, if you're measuring everything in centimeters, then your final answer (volume) will be cubic centimeters. If your answer is in feet, the your volume will be cubic feet.
