What size lampshade do I need?

It is important to get it right.  If your shade is too tall, it will make the lamp look too top heavy.  On the flip side, if the shade is too short it will make your lamp look out of balance.

Width of shade:

As a general guide, measure the widest part of the lamp base and times by 2 for the width of your shade.  If you have a square base lamp, measure diagonally across the base.

Height of shade:

For the height of your shade, it is 2/3 the total height of the base ie. 40cm high lamp would require a 26cm high shade.