How to Measure for a Storm Door Entry Door Swing Chart
"Swing" Chart
To determine 'swing', remember that your storm door will install to the outside of your entry door and will swing away from the entry door.  However, the handle of the storm door will be on the same side as the entry door handle.

So, your installation will either be 'Entry door is left hand swing' or 'Entry door is right hand swing'.
Storm door frames allow for a small degree of accommodation for the existing door opening. To be sure your new door fits correctly:
  •  From the outside looking in - find the dimensions from the inside edges of the entry door's brick molding (see illustration above). This is where your storm door will attach - the brick molding.
     
  •  Subtract about one inch from the width of the opening to arrive at the door width size. Any difference in the opening size can be easily adjusted and compensated for when you install the storm door frame.
     
  •  Measure the door opening height from top to bottom of the doorway (C), and the width at the top (A1), center (A2) and bottom (B3). If the width measurements vary, use the smallest measurement for specifying door size.

Hot Tip: "Brick mold" just means trim. Can be any material including wood or stucco.