AbstractBackgroundAcne is a concern in adults, especially in women. The specifications in current acne grading systems are not applicable to this particular population.ObjectiveTo develop and validate a measurement tool (AFAST: adult female acne scoring tool) for acne in women by taking into account the specific locations of adult female acne, and to evaluate the impact of the photographic modalities on rating reproducibility.MethodsSix experts in dermatology rated pictures of 54 women with a phototype from I to IV during two sessions, with an interval of 24 h. They rated the acne severity on the face using the GEA scale (Score 1) together with a new scale to assess acne on the mandibular zone (Score 2). Pictures of 30 women were taken using a standardized photographic device; pictures of the other 24 women were taken by their own dermatologists during daily practice.ResultsAt session 1, the inter‐rater's reproducibility was good for Score 1 with an ICC of 0.77 [0.72–0.83], and excellent for Score 2 with an ICC of 0.87 [0.82–0.91]. Between sessions 1 and 2, the mean intra‐rater's reproducibility was excellent for both scores with an ICC of 0.88 [0.84–0.92] for Score 1, and an ICC of 0.87 [0.78–0.92] for Score 2. Photographic modalities had no significant effect on the inter‐ and intra‐rater's reproducibility.ConclusionFor the first time, it has been demonstrated that AFAST can accurately rate acne severity in women. It is a promising, easy‐to‐use tool for both daily practice and clinical investigation.