Abstract. The accuracy of aperture area measurements is vital to many radiometric and photometric measurements. The Consultative Committee on Photometry and Radiometry (CCPR) undertook an international comparison of the methods by which member laboratories measure the areas of apertures used for radiometry. Nine laboratories measured eight different apertures varying in diameter size, fabrication method, material and edge type. This paper includes a description of the apertures used for the comparison, the results of the comparison categorized by artifact and by laboratory, and a brief discussion of the method used by each laboratory along with its uncertainty budget.

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The final report has been peer-reviewed and approved for publication by the CCPR, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).