Calculate the volume of numerous regular shapes with ease using our versatile volume calculator. Need to calculate the volume of a box? Try this tool. If you're wondering how to calculate the volume of a rectangular tank (also known as cuboid, box, or rectangular hexahedron), look no further! You may know this tank as a rectangular tank – but that is not its proper name, as a rectangle is a 2D shape, so it doesn't have a volume. where f f f is the height of the filled portion. Learn how to calculate the volume of a rectangular prism using the formula V = l × w × h, where l, w and h are the length, width and height of the prism. See solved examples and diagrams of different rectangular prisms. Online volume of rectangle calculation. Use this simple geometry volume of rectangle calculator to calculate volume.