Validated, reliable, globally-accepted outcome measurement instruments for hidradenitis suppurativa (HS) are needed. Current tools to measure the physical signs domain for HS rely on lesion counts that are time-consuming and unreliable.To assess the reliability and validity of the Hidradenitis Suppurativa Area and Severity Index Revised (HASI-R) tool, a novel method for assessing HS severity, incorporating signs of inflammation, and body surface area (BSA) involved.The measurement properties of the HASI-R tool were evaluated. The tool was created by combining the previously published HASI and Severity and Area Score for Hidradenitis (SASH) instruments. Twenty raters evaluated 15 HS patients in a hospital-based ambulatory dermatology clinic. The objectives of the study were to assess inter-rater and intra-rater reliability of the HASI-R and its components, as well as its construct and known groups validity. Existing lesion count-based clinician-reported measures of HS and their components were also assessed. Raters were also asked their preferences regarding the various HS severity assessment tools.The HASI-R had moderate inter-rater reliability (ICC = 0.60). This was better than all other HS physical sign outcome measures evaluated, which had poor inter-rater reliability (ICC < 0.5). HASI-R had the highest intra-rater reliability (ICC = 0.91). The HASI-R had good construct validity and demonstrated known groups validity. The HASI-R was also the most preferred tool by all raters.Results from the clinometric assessment of the HASI-R are encouraging, and support continued evaluation of this clinician-reported outcome measure.