How to calculate square footage for insulation

Accurate measurements of your home ensure you buy the correct amount of insulation and your rebate is accurate. Measure everything in inches and then divide by 144 to get the area in square feet. All calculations for your Power Smart Home Insulation Program rebate should be in square feet.

Wear protective equipment and clothing when working with insulation – check with your manufacturer or supplier for safety instructions. Take precautions if working in an area that contains hazardous materials (e.g. asbestos or lead).

Calculate attic area

  1. Measure the outside of your home.
  2. The interior attic space may differ (e.g., additions, varying levels of insulation). Separate into smaller spaces from the largest area.
  3. Multiply the length and width of each area.
  4. (A + B + C) ÷ 144 = total square footage.

Diagram of how to calculate area of your attic.


Calculate your wall cavity/exterior wall area

  1. Measure the outside of your home.
  2. Measure the height of the walls from the floor to the ceiling. If you own a multi-storey home, measure from the floor to the ceiling of the top storey.
  3. Measure the length and width of all exterior windows and doors.
  4. [(Exterior perimeter × height) − (window and door area)] ÷ 144 = total square footage.

Diagram of how to calculate area of your wall cavity or exerior wall.


Calculate your basement/crawlspace area

  1. Measure the inside of your home.
  2. Measure the entire perimeter. Measure the height of the walls from the floor to the underside of the subfloor.
  3. Measure the length and width of all exterior windows and doors.
  4. [(Interior perimeter × height) − (window and door area)] ÷ 144 = total square footage.

Diagram of how to calculate area of your basement or crawlspace area.

View insulation types and their R-values (PDF, 104 KB).