For bare die packages, the contact area is the area of the die. This is specified in the top-view perspective of the mechanical drawings. In this packaging type, the die is the highest point of the package and thus additional clearance to other points on the package like decoupling capacitors is not necessary. The following figure shows a top view of an example bare die. The value in red should be used to calculate surface area. Use the appropriate packaging and pinouts guide to find the values for specific devices.
The package height is denoted by the A dimension in the mechanical drawings. This represents the height from the seating plane to the top of the die. The associated table in the appropriate user guide specifies the min, max, and nom parameters. The following figure shows an example diagram denoting the A parameter used for height.