Convert all units to feet, and use the formula for a cylinder - pi x radius square x height (the height is the length in this case).
The volume of a pipe that measures 8 feet in length and 24 inches in diameter is: 25.133 cubic feet (about 188 US gallons).
1.96 cubic feet.
1.313 cubic feet.
1.963 cubic feet
1.96 cubic feet
Cubic inches measures volume. Square inches measures area. Therefore, you can not compare the two. It is like comparing feet and cups.
The volume of this cylinder is approximately 0.311 cubic feet.
The volume of this cylinder is approximately 3.41 cubic feet.
Those are incompatible measures
0.135 cubic feet
A 4-inch diameter pipe that is 3,000 feet long has a volume of: 261.8 cubic feet.
A 6-inch diameter pipe that is 16 feet long has a volume of: 3.14 cubic feet