1. A method for performing quantity takeoff computations, the method comprising: receiving a selection of a two-dimensional (2D) sheet included in a computer-aided design (CAD) drawing; receiving a selection of a quantify type and a quantify property for a takeoff object, wherein the quantify type specifies how instances of a first drawing object are quantified, and wherein the quantify property specifies a property of the first drawing object used to determine a value for the quantify type for a given instance of the first drawing object; including the quantify type selection and the quantify property selection in the takeoff object, wherein the takeoff object further includes cost data; associating the takeoff object with the first drawing object; receiving a selection of a first instance associated with the first drawing object included in the 2D sheet, wherein receiving the selection of the first instance comprises receiving a point located within the 2D sheet and encompassed by the first instance; quantifying, via one or more processors, the first instance to determine a first quantified value by at least determining a value of the selected quantify property for the first instance and calculating a value of the selected quantify type based on the determined value of the selected quantify property, wherein quantifying the first instance includes: determining a boundary associated with the first instance, determining a virtual area within the boundary, parsing the 2D sheet to determine a sheet scale, and calculating an area of the first instance by scaling the virtual area by the sheet scale, and setting the first quantified value equal to the area of the first instance; and computing a cost estimate for the first instance based on the first quantified value and the cost data.