In long wall and short wall method,

•  The wall along the length of the room is considered to be long wall and the wall perpendicular to the length of the room is considered to be short wall. 

•  To get the measurement of materials and work, length of long wall or short wall, centre line lengths of  individual walls is calculated first. 

•  Then the length of long wall, (out to out) may be calculated after adding half breadth at each end to its centre line length or we can say adding one breadth to the centre line length (in case of constant  thickness of wall) 

•  Thus the length of short wall measured in to in and may be found by deducting half breadth from its  centre line length at each end or we can say subtracting one breadth from the centre line length (in case of constant thickness of wall) 

•  These lengths are multiplied by breadth and depth to get quantities.