How to Measure Square Feet of a Room for Heating

Assess the shape of the room and decide whether it is a single rectangle or a more complicated shape. If the room is a rectangle with no additional nooks or bulges, treat it as a single area. However, if the room floor includes nooks, chimney breasts, bay windows and similar features, divide the area into a series of non-overlapping regular shapes, such as rectangles, triangles and segments of circles. For example a square room with a semi-circular window bay can be divided into a square and a semi-circle, while an "L" shaped room becomes two rectangles.

Use the following equations to determine the area of regular shapes.

Rectangle: Area = length x width
Triangle: Area = (length x width) / 2
Circle: 3.1415 x the radius squared
Semi-circle: (3.1415 x the radius squared) / 2

Calculate the area of each shape and combine them to obtain the total floor area. The result is the square footage of the room calculated for heating purposes.
For example, a room consisting of an "L" shape formed from two 10-feet-by-15-feet rectangles and a semicircular window bay with a radius of 4 feet has a floor area of 325.13 square feet -- (10 x 15) + (10 x 15) + ((3.1415 x 4^2)/2) = 325.13.