multiply the height of the window light (h) by 2 and add the width (a), then multiply the width (b) of the slat used by 4.
Length of batten on window with keystones
multiply the height of the window light (h) by 2 and add the width of the window light (a).
Length of cornice above window
multiply by two the width of the moulding used for the window (b) and add the width of the window light (a), then multiply the depth of the cornice (c) by 4 and add to the previous calculation.
Cornice length under sill
multiply by two the width of the moulding used for the window (b) and add the width of the window light (a), then multiply the depth of the cornice (c) by 4 and add to the previous calculation.
English 
Polish 
German