While beauty is partly about measurable characteristics, it is not only about that. Therefore, we cannot say that beauty is “just” about mathematically measurable attributes.
Recently, research has shown that there is some degree to which beauty is about things that can be measured. Specifically, it appears that beauty is connected to symmetry. People think that human faces and human bodies are more beautiful if they are more symmetrical.
However, this does not mean that beauty is “just” about mathematical proportions. We can see this in at least two ways. First of all, we know that standards of beauty can be different in different cultures. We know, for example, that American culture today values tanned skin whereas Japanese culture, among others, has valued paler skin as an indicator of beauty. We know that some cultures find women with more curves to be more attractive than women with fewer. Second, we also know that these values can change over time. Just since the 1920s, American visions of what a beautiful female body looks like have changed. The “flappers” of the 1920s wrapped their breasts to make them appear smaller. In the 1950s and 1960s, pinup models who were considered very attractive would be seen as heavy today as our society is obsessed with thinness.
Thus, beauty cannot be simply about mathematical proportions. It may be partly about that, but there are also culturally constructed aspects of beauty that are less susceptible to being measured.