A type describes a bulb that has a pear-like shape. The number that follows the “A” within the A series indicates the width of the bulb in one-eighth inch units or in millimeters.

What does Type A mean on a light bulb?

A type describes a bulb that has a pear-like shape. The number that follows the “A” within the A series indicates the width of the bulb in one-eighth inch units or in millimeters.

How do I know if a light bulb is type A?

A-shaped bulbs. “A” type bulb shapes are standard types for household lighting but you will see different variations and types of them. However, the standard bulb sizes are A19 and A60. The letter indicates the shape of the bulb but the number following it is the diameter of the bulb in eighths of an inch.