Ever wondered what are the exact dimensions of female lips that can be called as the most attractive?According to a study, a 50 per cent increase in lip size -- or in other words, the lips that made up about 10 per cent of the lower third of the face was the most preferred.To assess the most attractive lip dimensions of women, the researchers from the University of California - Irvine used focus groups and morphed computed images to try to find out because established guidelines may help achieve optimal outcomes in lip augmentation.The faces of white women were ranked for attractiveness with varied lip surface areas created for the faces and upper to lower lip ratios manipulated.The findings, published online by JAMA Facial Plastic Surgery, showed that lips with a 53.5 per cent increase in surface area from the original image with a one-to-two ratio of upper to lower lip that make up about 10 per cent of the lower third of the face were deemed to be the most attractive."We advocate preservation of the natural ratio or achieving a 1:2 ratio in lip augmentation procedures while avoiding the overfilled upper lip look frequently seen among celebrities," said Brian J.F. Wong, from the University of California.Researchers said they hoped the study would help establish guidelines to achieve optimal outcomes in lip augmentation.