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How to Measure a Lampshade

Ralph Lauren Architect Floor Lamp
Back to More about lampshades – and this time, we are talking about how to measure a lampshade. A very important piece of finding the right shade!

Customers come into our store everyday looking for a replacement lampshade.  Ideally, the lamp requiring the new shade should accompany the customer – it makes for a much more single and successful trip to the store; without the lamp – or at least the exact dimensions of the existing lampshade, we are guessing at selecting a shade that will fit the lamp;  my track record is not great without the lamp, but very often spot on with the lamp.

Lampshades are measured and sized using the diameters of the top and bottom as well as a side measurement:

Lampshade Sizing

  • A – the width across the top of the shade
  • B –  the width across the bottom of the shade
  • C – the slant height down the side of the shade
  • D – the distance from the bottom of the shade to the washer in the center of the top ring (on most shades, this measurement is generally about 3/4” less than the height from the top of the shade to the bottom of the lampshade; however, on larger shades the washer is often recessed several inches)

The width across the bottom is also the “size” of the lampshade – an 8” lampshade or a 15” lampshade.  The top dimension is important to the shape of the shade – it does not directly contribute to how the lampshade will fit the lamp.

Blue and white lamps 2
The side dimension is very important in fitting the lampshade to the lamp.  Most US made lamps and lampshades “attach” to the lamp by sitting on a harp; the height of the harp is determined based on the vertical height of the lampshade.  A lampshade whose bottom edge sits below the socket and harp saddle and above the top of the base of the lamp, is correctly “fitted” to the lamp.  Most well designed lamps have a small piece between the top of the lamp and the bottom of the harp – known as a lamp “neck”.  Ideally, the bottom of the lampshade will land somewhere along the neck ensuring the lamp-works are not visible but above the top of the lamp so that the top of the lamp base is not obstructed by the bottom of the lampshade.