bulb size

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What you see

Brightness (lumens)
CRI Color Rendering Index
Color Temperature (Kelvin)

Energy Use
Energy Cost

Bulb Specs
Bulb size
Base type
Bulb finish
Understand Bulb size and shape

  When looking at different bulbs, (which in industry terms are referred to as "lamps") you will see a few numbers and letters that help explain what bulb you are looking at. But the layman may not be familiar with these terms, and it often falls to those inside the lighting industry to look at the bulb that is being replaced to find a suitable replacement. The shape of the bulb has been converted into a number, so that lighting professionals can know at a glance exactly what type of bulb is needed. The attached chart helps demonstrate what the bulb shapes are, and what they stand for.

  In addition to different bulb shapes, the designation for a particular bulb is usually followed by a number for instance an A19 bulb or a PAR30. Those numbers refer to the width of a bulb measured in 8ths of an inch. So an A19 bulb would be An A-shape bulb (arbitrary) that is 19/8" in diameter which is 2 and 3/8". The PAR30 would be a directional sealed beam lamp that is 30/8" in diameter or 3 and 6/8".