A-series light bulb

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An A-series light bulb

The A-series light bulb is the "classic" type of light bulb that has been the most commonly used type for general-purpose lighting applications since the early 20th century. It has a pear-like shape and an Edison screw base. The number that follows the "A" within the A series indicates the width of the bulb in one-eighth inch units in North America[1][2][3] or millimeters in India and Europe.[4][5]

Physical outline[edit]

The most commonly used A-series light bulb type is the A19 bulb (or its metric equivalent, the A60 bulb[2][4]), which is 198 in (2 38 in; 60 mm) wide at its widest point[3] and approximately 4 38 inches (110 mm) in length.[6] Another common A-series light bulb type is the A15 bulb which is commonly used for appliances and ceiling fans. The A15 bulb is 158 in (1 78 in; 48 mm) wide at its widest point.

Socket type[edit]

Most A19 light bulbs come with an one-inch long Edison screw base, either of type E26 (i.e. 26 millimeters in diameter) in countries with a mains voltage of 100–120 volts, or of type E27 (i.e. 27 millimeters in diameter) in countries with 220–240 volts AC. A-series light bulbs using the older B22 bayonet twist type base are less common; they can be found in the UK and many British Commonwealth countries.


Philips L Prize bulbs count as A19 under Energy Star requirements.

ANSI C79.1-2002, IS 14897:2000,[4] and JIS C 7710:1988[7] define the "A shape" as "a bulb shape having a spherical end section that is joined to the neck by a radius", where the radius is greater than that of the sphere, corresponds to a osculating circle outside the light bulb, and is tangent to both the neck and the sphere. The Energy Star certification only requires omnidirectional light bulbs to fit the overall dimensions of the corresponding ANSI bulb type.[8](14.1)

Lamp types[edit]

An A60 (A19) LED light bulb with E27 screws

Although most A-series bulbs have historically used incandescent lighting technology, some other technologies – such as Compact Fluorescent (CFL) or LED lamps – have been used in A-series bulbs more recently.

See also[edit]


  1. ^ "Lamp Size and Comparison Features" (PDF). WW Grainger Inc. Lamp size (maximum lamp diameter) is expressed by a number representing eighths of an inch.
  2. ^ a b "LED University: Light Bulb Shapes and Sizes Explained". EagleLight. 'A' type bulb shapes are standard house hold light bulbs. The number after the bulb shape is the number of eighths of an inch in diameter. For non-imperial measured bulbs the number following the bulb shape is the number of centimeters [sic] at the widest point of the bulb. Standard bulb sizes include A19 for imperial measurements and A60 for a slightly smaller metric measured bulb.
  3. ^ a b "Light Bulb Reference Guide". Superior Lighting. The letter indicates the shape of the bulb and the number relates to the diameter of the bulb in eighths of an inch. The most commonly used household bulb is the A-19.
  4. ^ a b c "IS 14897 (2000): Glass Bulb Designation System for Lamps - Guide". Retrieved 21 March 2017. A bulb shape having a spherical and [sic; end?] section that is joined to the neck by a radius [...] A60: An “A” shape bulb with a nominal major diameter of 60 mm.
  5. ^ "LED Start GLS: 40, 60, 75 & 90w equivalents" (PDF). GE Lightling.
  6. ^ "Light fixtures and light bulb sizes". www.tuxgraphics.org. Retrieved 28 February 2017.
  7. ^ "JIS C 7710:1988 電球類ガラス管球の形式の表し方" (in Japanese). Retrieved 2017-03-21.
  8. ^ "ENERGY STAR Eligibility Criteria Version 2.0, Rev. Oct-2016" (PDF). Retrieved 2017-03-21. Lamp shall comply with ANSI minimum overall length (min OAL), maximum overall length (MOL) and maximum lamp diameter values, where they exist