How to Identify Light BulbsLight bulbs are measured in several ways. Physical dimensions, amount of
light output, wattage consumption are just a few. This post will focus
on the physical dimensions of light bulbs and the differing types of
bases. There are four ways of measuring a bulbs physical dimensions:
- Bulb shape: bulb shapes vary, from pear shapes to funnel shapes to tube
shapes. Each has a designation. Examples include: PAR for parabolic
aluminized reflector or T for tube. Many household halogen lights are a
MR16, the MR is for 'metallic reflective'.
- Bulb diameter: bulb
diameter is measured in 1/8 inches increments at the maximum point of
diameter. A PAR30 is 30 eighths of an inch in diameter or 3 3/4 inches. A
T8 is 8 eights of an inch in diameter or 1 inch.
MR16 is 16 eighths or 2
inches in diameter.
- Bulb length: bulb length is measured in inches as
the Maximum Overall Length (MOL). So a 4 foot florescent tube has an MOL
of 48 (inches).
- Bulb base type: Bases are measured in millimeters. So
a typical household screw-in base like
E27 (E is for Edison Screw-in) is
27 millimeters in diameter. An E11 candelabra base is an 11 millimeter
diameter Edison screw in base. For pinned bases like a florescent tube or
a pinned MR16 halogen bulb, the measurement is from the center of one
pin to the center of the other pin.
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