Calculating the pole length

After take the original curtain width - the first measurement from the wall - and add twice the pole projection beyond the end of the curtain to get the cut length of the aluminium pole itself - this is plus 59 x 2 mm.
The pole has a pulley housing at each end that will add another 31 x 2 mm - shown by dotted lines in the diagram. Finally, add the net finial length twice to get the overall size of the finished pole.

Use the net finial length to calculate the total overall length of the pole and make sure that it fits correctly on the wall free from obstruction.

Pole matches the wave sizes:
Two-way draw, each curtain is 400 mm wide = 800 mm total width. The pole excluding finials adds 90 mm to each end = total 980 mm

Adjustment:
If the full curtain width needs to be narrower - say 720 mm - the pole reduces in length by 80 mm and the curtain concertinas down in size. The workroom sizes for both curtains is the same.

If you haven't check the pole for wave curtain, please refer to the page of "Calculating the curtain width with waves".