Rectangular Prism Calculator - Volume, Area, Diagonal

A rectangular prism, also called a cuboid, is a three-dimensional solid with six rectangular faces, twelve edges, and eight vertices. Everyday examples include shipping boxes, books, rooms, storage containers, and many building components. Because the shape is so common, its measurements show up constantly in geometry classes, architecture, engineering, manufacturing, packaging, and construction planning. The most familiar measurement is volume. For a rectangular prism, volume is found by multiplying the three perpendicular dimensions: length × width × height. This tells you how much three-dimensional space the prism occupies. If the dimensions are measured in meters, the volume is measured in cubic meters. Volume matters when you need to know capacity, storage space, material fill, or shipping size. Surface area is the total area of all six faces. The formula 2(lw + lh + wh) adds the areas of the three distinct face pairs and doubles them because each face type appears twice. Surface area is important when estimating paint, wrapping material, insulation, sheet metal, or any covering needed for the outside of a box-shaped object. A rectangular prism also has several diagonals. The space diagonal runs from one vertex to the opposite vertex through the interior of the solid. Its length is √(l² + w² + h²), which is a direct extension of the Pythagorean theorem into three dimensions. Each rectangular face has its own diagonal as well: √(l² + w²), √(l² + h²), and √(w² + h²). These face diagonals are useful when checking bracing distances, screen sizes, panel cuts, and diagonal supports on individual faces. This rectangular prism calculator combines all of those measurements in one place. Enter the length, width, and height, and the tool instantly reports the volume, surface area, space diagonal, and all three face diagonals. That makes it useful for students checking homework, teachers preparing examples, engineers reviewing dimensions, or anyone comparing box-like shapes quickly and accurately.