If you want an easy way to compute the volume of things, a good place to start is to memorize that there are **231 Cubic Inches in a gallon**.

If you can figure out the square area of rectangular tank or can find the size of a circle and multiply the area times the height, you can figure out the volume.

Once you have Gallons figured out it is easy to get to Barrels, just divide by 42 (there are 42 gallons in a Bbl)

Bbls is the abbreviation for Barrels; just a bit of helpful history…

# History of the 42-Gallon Oil Barrel