Simply put, the rule of three suggests that things grouped in groups of three are more natural, harmonious, and visually appealing. Odd numbers challenge our brain a bit and are more interesting. The Latin phrase “omne trium perfectum” means “everything that comes from three is perfect, or every set of three is complete”. And when it comes to design, that definition fits perfectly.
Our eyes are naturally drawn to groups of three. The rule, or guideline if you prefer, simply states that things ordered in odd numbers are more visually appealing to the human eye. Our brains love odd numbers because they challenge us mentally. Clusters of elements in odd numbers tend to seem dynamic and more natural to us.
Whereas things that are grouped in even numbers tend to seem stale, “staged” and cold. Three seems to be the magic number for interior design, but the rule also applies very well to groups of five or seven. In addition, the rule of “odd numbers” not only applies to interior design, but the principle is reflected in many other areas of life, from architecture to photography, and even in religion. To create a group of three people in a sophisticated way, follow the example of British interior designer Sophie Paterson.
If you look at design magazines or home catalogs, you'll notice that often the furniture in the living room is arranged in groups of three.
