Summary
A smaller ratio of upper-lip to lower-lip is considered a feminine feature, while a larger ratio is a masculine one. Research across various studies reveals interesting differences between male and female lip structure and their perceptions. Kar et al. (2018) found that women’s upper lip area is dominated by the fuller, colored part, making it more noticeable. This leads to a smaller upper to lower lip ratio, which signifies a fuller or larger lower lip, seen as feminine and attractive. Altman (2012) supported this, stating women have fuller, shorter upper lips, and both lips are equally thick, resulting in a smaller upper to lower lip ratio, seen as a feminine trait. In contrast, Lakhiani & Somenek (2019) found men to have a thinner colored part of the upper lip, making their upper lip less full than their lower lip. This leads to a larger upper to lower lip ratio, seen as a masculine trait.
Research
The study by Kar et al. (2018) found that while the thickness of the upper and lower lips (the vermilion heights) are generally similar in both men and women, the upper lip vermilion makes up a greater proportion of the entire upper lip in females compared to males. This implies that the upper lip area in women tends to be dominated by the fuller, colored part, making it appear more prominent.
In addition, the study suggested that fuller lips, particularly a larger lower lip, are more attractive and considered more feminine. This leads to a smaller ratio of the upper lip to the lower lip in females, meaning the lower lip is relatively larger or fuller. This also aligns with a common perception that facial features which are fuller or ‘baby-like’ are often seen as feminine and attractive. So, a smaller ratio of the upper lip to lower lip, with a fuller lower lip, is considered a feminine feature because it’s often associated with attractiveness in females and follows typical societal preferences for feminine beauty.
A study indicated that women typically have fuller, shorter upper lips (Altman, 2012), with the upper lip and lower lip about equal in thickness. This equality results in a smaller upper-lip to lower-lip ratio, a characteristic deemed feminine. Men, on the other hand, tend to have a thinner vermilion portion (the colored part of the lip) compared to the cutaneous segment (the skin part), making their upper lip less full than their lower lip (Lakhiani & Somenek, 2019). This discrepancy leads to a larger upper-lip to lower-lip ratio, a feature seen as masculine.
Reference
Kar, M., Muluk, N. B., Bafaqeeh, S. A., & Cingi, C. (2018). Is it possible to define the ideal lips?. Acta Otorhinolaryngologica Italica, 38(1), 67.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5952987/
Altman, K. (2012). Facial feminization surgery: current state of the art. International journal of oral and maxillofacial surgery, 41(8), 885-894.
https://www.sciencedirect.com/science/article/abs/pii/S090150271200197X
Lakhiani, C., & Somenek, M. T. (2019). Gender-related facial analysis. Facial Plastic Surgery Clinics, 27(2), 171-177.
https://www.facialplastic.theclinics.com/article/S1064-7406(19)30006-9/fulltext