HINTS AND TIPS
CHOOSING THE RIGHT SIZE LAMPSHADE
The good news is that there are no hard and fast rules. The bad news is that there are no hard and fast rules! When it comes to lampshades, beauty is in the eye of the beholder. Some like their lampshades to sit like large hats on the base, and others prefer the shade to lift up from the base like an arrow. For those who are not sure what they like, there are some considerations and some guidelines that can direct the decisions.
One consideration would be where the lamp is going to live. If the lamp is going to be in a thoroughfare, where people sweep through going somewhere else, then a large shade will be a nuisance and could get knocked about. Better then to choose height over width. If the lamp is going to be low down on a table, it may look wrong when you look at it from a standing position; the shade may look as if it is consuming the lamp, and much too big for the base. This although the proportions will look perfect when seen from a sofa or armchair - in line with the lamp. Another consideration would be what the lamp is there for. If it is so you can read next to it, then you must consider the height at which the light comes out. For example, in my childhood, bedside lights were traditionally small with tiny empire shades. More there to light the way than to read by. A book buff like me wants high lamps on the bedside table, so that I can see the tiniest of fonts even if the wattage is low.
The other guidelines we can use in choosing a shade are:
The lampshade must cover the lightbulb fixture of the lamp.
The lampshade should not be larger than half the height of the lamp base, or it may look overwhelming.
The bottom of the shade ought to be wider than the width of the base.
A traditional guideline is for the height of the shade to be just under half the height of the base, and the diameter of the bottom ring of the lampshade 4/5 of the height of the base.
All that said - they are only guidelines, and what looks good will look good whether it follows them or not!