PrettyScale measures the face beauty by studying and testing the placement and sizes of different face features. The results are based on the face shape, distance between eyes and lips, mouth size and face symmetry. Sometimes golden ratio is also used in determining the results. Results can be different based on how you place lines and dots on your face according to instructions.
Helen is considered the unit for measuring beauty. It is a humorous unit based on the story of Helen of Troy (or Helen of Sparta). She waas the daughter of Zeus and Leda. In Greek myths she was considered the most beautiful woman in the world. She had a face that lauched a thousand ships. So one Helen means a face that can launch a thousand ships. Helen is a very big unit and in practice a smaller unit micro Helen is used. On prettyscale.com if your face gets 80% score that means 80 micro Helen.