Cuboid Volume Calculator

How it is calculated

You enter the three edges of a rectangular box, l (length), w (width) and h (height), all in the same unit. The tool returns the volume V = l × w × h, the total surface area SA = 2(lw + lh + wh) and the space diagonal d = √(l² + w² + h²). Each value is rounded to two decimals.

All three edges must be greater than zero. Results are labelled only as units, units² and units³: if you typed centimetres, the volume is in cubic centimetres, the area in square centimetres and the diagonal in centimetres. The order of length, width and height does not change any result. The surface area counts all six faces and ignores wall thickness, so it is the outer area of the box.

Common mistakes

• Mixing units, for example length in metres and height in centimetres; the volume is then off by a factor of 100 or more.
• Reading the volume as a capacity of the inside when you measured outer edges; wall thickness makes the usable inner volume smaller.
• Adding the three edges or multiplying only two; volume needs all three, and the surface area is a different quantity measured in square units.
• Confusing the space diagonal with the diagonal of one face: the face diagonal ignores the third edge and is always shorter.
• Converting units after the calculation by the linear factor; cubic units scale with the cube (1 m³ = 1,000,000 cm³, not 100).