Which Cell Size Should I Pick?
Manufacturers carry cellular shades in a variety of cell sizes ranging from 3/8" all the way up to 1 1/4". Cell size is measured as half the width of the compacted stack of cells in the fabric. The wider the width, the larger the cells are when hanging.
In general, select a larger cell size for larger windows and a small cell size for smaller windows to maintain proper proportion.
Double cell cellular shades are most times made of 2 layers of 3/8" cellular material joined together although some manufacturers use 1/2" single cell material for their double cell cellular shades.
When assessing which size to order, consider all the window sizes in a given room. If most windows are small (less than 40" w x 48" h) select a 3/8" cell size. If your windows are larger than that, select a 3/4" cell size. For windows larger than 70" w x 84" h consider the 1 1/4" cell size.