Step 1: Measure Length, Width, and Height To get started, you’ll need a tape measure or ruler. Measure the length, width, and height of the object in feet. 5 juin 2023 · So, how do we calculate its volume in cubic feet? Let's find it using to two methods we outlined in the paragraph above: Step 1: First, to calculate cubic feet from inches, we need to convert the inches into feet: Width = 30 in / 12 = 2.5 ft \text{Width} = 30\ \text{in} / 12 = 2.5\ \text{ft} Width = 30 in /12 = 2.5 ft;.