Abstract: The present invention is a single apparatus that can be adjusted through a range of diameters to measure an anatomical tissue annulus. The apparatus includes an elongated support member having a proximal end and a distal end. An operator actuated movable member is joined to the proximal end of the elongated support member while an adjustable member is joined to the distal end of the elongated support member. The adjustable member has a reference axis and an outer curved surface selectively positionable in response to the operator actuated member. In particular, the outer curved surface can be selectively positioned between an inner position proximate the reference axis and an outer position spaced apart from the reference axis.