Methods for determining the straightness value of a hairstyle are provided. In accordance with an embodiment, a method comprises: defining at least one hair analysis region in a digital image in which hair is depicted; ascertaining hair profiles of the hair depicted in the at least one hair analysis region, wherein the hair profiles of all hair depicted in the hair analysis region form a totality of the hair profiles; ascertaining a main direction of the hair profiles; and ascertaining the straightness value of the hairstyle on the basis of the main direction of the hair profiles and the totality of hair profiles.