Architects and designers have often used computational design techniques in their design process, even without “computers”, from designing spaces which activate at the instant of the solstice sunrise, to creating geometrically complex and structurally innovative cathedrals. Designing with rules and variables can lead to solutions which satisfy the design criteria and may result in interesting and unanticipated models. Computational design is a process of designing and a way of thinking, contemporary tools can promote and enhance this process. Algorithmic and parametric modelling (and thinking) can be powerful processes in design, and particularly in working with complex geometry and addressing project constraints and analytical and data-driven design. This paper describes these methods and provides examples of their use on projects at Skidmore, Owings & Merrill.