Concrete lintels are vital structural members used in masonry construction for support above window and door openings. Although these masonry components are complicated to design, calculating their volume can be easy enough for almost anyone with basic tools.
Things You'll Need
 Building plan (structural floor plan)
 Architect scale
 Calculator

Measure the length of the lintel using the architect scale set to the sheet's scale factor, and convert this measurement to inches (multiply by 12) to make later steps easier.
Example: A lintel that is 2 feet in length can be converted to 24 inches.

Locate the lintel size; this will be printed on the sheet, next to the lintel. The lintel size is the height and width, and will be in inches. Multiply these dimensions to find the cross sectional area.
Example: If the size note indicates the lintel to measure 8 by 16 inches, it will have a cross sectional area of 128 square inches.

Multiply the lintel length by its cross sectional area to find the volume in cubic inches.
Example: The lintel measuring 24 inches in length, with a cross sectional area of 128 square inches, will have a volume of 3,072 cubic inches.

Divide the volume calculated in Step 3 by 144 to find the total volume of the lintel in cubic feet.
Example: The lintel with a volume of 3,072 cubic inches, divided by 144, will have a total volume of 21.3 cubic feet.