Embodiments of the present disclosure provide a workpiece singulator with one or more movable stairs. A first one of the movable stairs may include an outer step member and an inner step member that is positioned between the outer step member and a second one of the movable stairs. The step members may be movable synchronously as a single stair to transport larger workpieces and asynchronously to transport smaller workpieces on the outer step member. Optionally, the workpiece singulator may further include a sensor configured to detect the size and/or position of a workpiece. In some embodiments, the workpiece singulator may be coupled with a controller configured to control the position of the outer step member independently of the position of the inner step member. In various embodiments, a workpiece singulator as disclosed herein may be operable to selectively singulate workpieces of different sizes.