The Area tool measures surfaces such as floors, slabs, wall faces on elevations, roofing, and site areas.
Check the drawing scale.
Select Area in the bottom toolbar.
Trace the perimeter, or use Draw boxes for a rectangle.
Click Finish or press Enter.
Name the measurement in Properties.
Use Cutout to subtract openings or excluded areas. Use Add area to group more rooms under the same named measurement. Review the total in Quantities.
Properties also offers Volume and Slope when you need those calculations. Set the relevant dimensions or slope to match the drawings.