If you have access to a vacuum sealer, you may be able to seal a small object in a watertight plastic coating with minimal air inside. This will allow you to get a good estimate of volume since the volume of the plastic used is likely to be relatively small compared to the volume of the object.
It’s a good idea to locate a dry towel as well, since the object will be dripping water when removed from the container.
If you are using a graduated cylinder or measuring cup with volume measurements on the side, you do not need to make a mark. Just look for the volume measurement at the water’s surface, and write this number down. [3] X Research source
When you take the volume of the heavy item alone, include anything you used to attach it to the original object, such as safety pins or tape.
Do not measure the height of the entire container, just the height from one water mark to another. Use this online calculator or search for another “rectangular prism calculator” that can multiply these numbers for you.
Calculate πr2, or π x the radius x the radius, to find the area of a circle across the cylinder. If you don’t have a calculator with a π button, find one online or estimate by replacing it with 3. 14. Multiple your answer by the height between the water marks (which you measured at the beginning of this step) to find the volume of space the water took up. This answer is also the volume of your object. You can get a more precise answer, or save yourself some math, if you enter your measurements on an online cylinder volume calculator.
Look for places where the irregular object is joined together at an unstated angle (not 90º). Can you “cut it apart” at that angle into two objects that have names, such as cylinders or pyramids? These do not have to be the same object. [10] X Research source
If the word problem tells you the diameter but not the radius, divide the d iameter by two to get the radius. You may need to do some addition or subtraction to find the measurements you need. For instance, say the problem tells you “a building shaped like a cone on top of a cube has a height of 30 units, but the height of the cube section is only 20 units tall. " The height of the cone isn’t listed, but logically it must be 30 units - 20 units = 10 units.
If you need a refresher on how to calculate volumes, see these instructions for common shapes.
