What makes a face beautiful? Perfect skin? Big eyes? A large smile? All these play a role, but in the aesthetics industry the answer is a mathematical ratio, dating back 2,500 years.

Some 2,500 years ago, in Ancient Greece, it was discovered that when a line is divided into two parts in a ratio of 1: 1.618, it creates an appealing proportion. This ratio is known as the golden ratio, the divine proportion or phi (named after Phidias, a Greek sculptor and mathematician who used this ratio when designing sculptures).

Since the Renaissance period, artists like Botticelli and Leonardo Da Vinci have used the golden ration in the sketching of their paintings, such as Monalisa or Birth of Venus. During modern times, the golden ratio has been applied to facial beauty and adopted as a guideline for aesthetic treatments.

We may be unaware of it but we subconsciously judge beauty by facial symmetry and proportion. Cross-cultural research has shown that no matter the ethnicity, our perception of beauty is based on the ratio proportions of 1.618. As the face comes closer to this ratio, it is perceived as more beautiful. As an example, the ideal ratio of the top of the head to the chin versus the width of the head should be 1.618.

This ratio is used to mark out the ideal proportions on a patient’s face and aesthetic enhancements that ignore phi may make patients look worse.

How do we use the golden ratio to measure the ideal facial proportions?

• the distance from the top of the nose to the centre of the lips should be 1.618 times the distance from the centre of the lips to the chin
• the hairline to the upper eyelid should be 1.618 times the length of the top of the upper eyebrow to the lower eyelid.
• the ideal ratio of upper to lower lip volume is 1:1.6 (the lower lip should have slightly more volume than the upper lip)