Background <p>Nursing acuity measurements refer to the assessments of the intensity of nursing care required by a patient, helping to determine appropriate levels of nursing resources and staffing requirements. The aim of this paper is to describe the development and validation of a tool for measuring nursing acuity within adult somatic in-patient care settings, distinguishing between advanced nursing tasks and basic nursing tasks.</p> Method <p>The nursing acuity tool was developed through an iterative process in the context of a Swedish healthcare region. The methodological process involved a literature search, exploration of non-validated tools used within Swedish healthcare, and nursing staff discussions to reach a conceptual tool. This tool underwent pilot testing across five wards, as well as testing for content- and construct validity, and inter-rater reliability.</p> Results <p>After an iterative process of development and testing, we reached a final version of a tool, subsequently named the Swedish Nursing Acuity Measurement (NAM-S). The results demonstrated acceptable validity and inter-rater reliability.</p> Conclusions <p>Our study provided support that the NAM-S can be used for assessing nursing acuity within adult somatic in-patient care. To refine the model, further examinations of its usefulness and experiences of the practical use of NAM-S are warranted.</p>