An adjustable square has a blade including a scale, a body, a slot formed in the body for movably receiving the blade, a locking mechanism operably engaged with the body for releasably securing the blade within the slot, and an indexing member operably engaged with the body and operably engaged with the blade. The indexing member indexes the body at precise locations along the blade. A method for indexing an adjustable square is also provided. The method includes positioning a body of the adjustable square at a precise known position and indexing, with an indexing member of the adjustable square, the body of the adjustable square at the precise known position.