A rectangular prism is a solid shape with six rectangle faces and three dimensions. Some people also call them an oblique, a cuboid, or a rectangular hexahedron. A right rectangular prism is also an acceptable term. The shape can have sides that lean to one side as well.

To work out the volume of a rectangular prism, you need to use the formula below.
In the formula, you will see three letters = h, w, and l.
H = height
W = width
L = length
The formula is *h x w x l*
Let’s say you want to find the volume of an apple carton. Follow these steps with example measurements below.
1. Identify the length of the box - 20 inches long
2. Identify its width – 18 inches wide
3. Measure its height – 13 inches high
4. Calculate the cuboid volume
*Volume = 13 x 18 x 20 = 4,680 in³*

Identifying the area of a rectangular prism involves a long-winded sum, but it’s as effortless as determining the volume – especially with a **rectangular prism calculator**. As you know, the prism has six faces which include three parallel rectangle pairs. Add all the faces together to get the surface area.
The formula is as follows:
*Surface area = 2 x (h x w) + 2 x (h x l) + 2 x (l x w) = 2 x (h x w + h x l + I x w)*
Using the same dimensions of the apple carton above, we’ll work through it step by step.
1. Calculate the surface areas
*Height x width = 13 x 18 = 234 in²
Height x length = 13 x 20 = 260 in²
Length x width = 20 x 18 = 360 in²*
2. Add all figures together then divide by two
*260 + 360 + 234 / 2 = 427 in²*
The apple carton’s surface area is *427 in²*.
Alternatively, you can use a rectangular prism calculator instead of having to work the value out by hand.

If you want to know the diagonal value of a rectangular prism, then you will see it’s a fairly straightforward process.
**Use this formula:**
*Diagonal = √ (l² + h² + b²)*
The formula is very similar to that in use with the Pythagorean theorem.

Did you know the rectangular prism is not the only shape for which you can use a calculator to get the volume? There are several others. If you ever need to find the volume of a cone, pyramid, sphere, or any other three-dimensional shape, there is sure to be a calculator to help.