Light Bulb Shapes Guide

The names of light bulb shapes are denoted with a letter, which describes the shape, and a number, which indicates the size.

The number associated with the shape indicates the diameter of the light bulb at its widest part in eighths of an inch. For example, an A19 light bulb has a maximum diameter of 19/8 of an inch or 2.375 inches.

Light bulb shapes chart

lk_shape_a A – Appliance light bulbs

Appliance light bulbs are one of the most widely used shapes and can be used almost anywhere, including homes, hotels, and restaurants. Appliance light bulbs have the shape that most consumers think of when they picture a light bulb. Typical sizes include A15, A19, A21, and A23.

  PS – Pear shape light bulbs

Pear shape light bulbs are similar to A light bulbs, except they have a larger diameter, which causes the bulb to look like a pear. Typical sizes include PS30 and PS40. PS30 light bulbs can be found in office buildings and retail stores, whereas PS40 light bulbs are used in radio towers, cellular towers, bridge power lines, and high tension wires.

lk_shape_s S – Sign light bulbs

Sign light bulbs are found in outdoor signs used by casinos, hotels, restaurants, and theatres. Typical sizes include S6, S11, and S14.

lk_shape_c C – Candle light bulbs

C light bulbs are made to look like a candle flame for decorative applications, such as chandeliers, restaurants, bathrooms, and hotels. C light bulbs with a blunt tip are sometimes referred to as “torpedo shaped” or “bullet,” as with most compact fluorescent C light bulbs and C-7 incandescent bulbs. C light bulbs with a molded, bent tip (also known as a flame tip) are sometimes referred to as a “chandelier light bulb.” The bent tip is created in order to give the light bulb a more aesthetic appeal. The C7 is used in marquees, time/temperature signs, and scoreboards. The C9, C11, and C15 are used in decorative applications.

lk_shape_f F – Flame light bulbs

F light bulbs are similar in size and shape to C light bulbs; however, the glass of the bulb is blown and/or etched in such a way that causes the light to look as though it is flickering like a flame. F light bulbs are used in decorative applications such as chandeliers, bathrooms, and restaurants.

lk_shape_h H – Chimney light bulbs

Chimney light bulbs are found in decorative applications such as coach lights and post lights. The most common size is H19.

lk_shape_g G – Globe light bulbs

Globe light bulbs are found in decorative applications, such as bathrooms, theatres, restaurants, and hotels. Typical sizes include G16.5, G25, and G40.

lk_shape_r R – Reflector light bulbs

Reflector light bulbs have a built-in reflecting surface, which causes the light to be pushed through the front of the light bulb, as opposed to being emitted around the entire bulb. Reflector light bulbs are used for down lighting, and they are used primarily in recessed cans or track lighting for residential, retail, hotel, and restaurant applications. The most common size is R20.

lk_shape_br BR – Bulk Reflector light bulbs

BR light bulbs were created in response to EPACT, which mandated that reflector light bulbs needed to meet minimum efficiency standards. Standard reflector light bulbs in higher wattages and sizes lost light in the neck and sides of the light bulb. The bulk reflector in the neck of the light bulb redirects the light lost in the neck and reflects it forward to increase the overall lumen output of the light bulb, allowing light bulb manufacturers to continue producing the larger reflector light bulbs and still abide by EPACT laws. Typical sizes include BR30 and BR40. These light bulbs are used for down lighting in recessed cans for residential, hotel, food service, offices, and restaurant applications.

lk_shape_er ER – Elliptical Reflector light bulbs

ER light bulbs were also created in response to EPACT. In this case, the elliptical reflector increases the overall lumen output by redirecting light that has been lost at the sides of the light bulb and reflecting it forward. The most common size is ER30. These light bulbs are used for down lighting in recessed cans for residential, hotel, and office applications.

lk_shape_par PAR – Parabolic Aluminized Reflector light bulbs

PAR light bulbs are reflector light bulbs that have an aluminized reflector in a parabola shape. They are covered with a hard glass lens to control the light beam, which is available in a variety of beam spreads from narrow spot to wide flood. PAR light bulbs can be used outdoors unprotected because their hard glass shell can withstand adverse weather. PAR light bulbs are also used for down lighting applications in recessed cans and track lighting in residential, retail, museums, and art gallery applications. Typical sizes include PAR16, PAR20, PAR30, PAR30 long neck, and PAR38. The PAR30 long neck was introduced to replace incandescent BR30 light bulbs in recessed cans in which standard PAR30 light bulbs did not fit.

lk_shape_par MR – Mirror Reflector light bulbs

MR light bulbs have a mirrored reflector. They are used for accent and spotlighting in various retail, residential, and commercial applications. The most common size is MR16; however, MR11 is also used in limited applications.

lk_shape_t T – Tube light bulbs

T light bulbs are shaped like a cylindrical tube. Depending on the size, T light bulbs have very different applications. Incandescent T6 light bulbs are used in exit and stairway signs and picture lights. Linear fluorescent T12, T10, T8, and T5 light bulbs come in a variety of lengths, ranging from 2-8 feet. These light bulbs are placed in fluorescent troffers and are used for general lighting in offices, retail outlets, hospitals, and parking garages. High-intensity discharge light bulbs also come in T shapes, including T9 and T15. These light bulbs are used in sports arenas, billboard signage, and industrial applications.

lk_shape_u-bend U-Bend – U-Bend Tube light bulbs

The U-Bend T8 is created by bending a 4-foot length T light bulb into a U shape in order to reduce the maximum overall length of the light bulb. This is desirable in some locations that have limited space. By bending a 4-foot light bulb into a U configuration that is comparable to a 2-foot light bulb in length, the end user will receive double the light output in the smaller space. This light bulb is used in offices, hospitals, and retail applications.

lk_shape_spiral Spiral – Spiral Tube light bulbs

The spiral light bulb is the shape of a compact fluorescent light bulb. A smaller diameter fluorescent T light bulb, such as T4, T3, T2, or T1, is twisted into a spiral or coil configuration in order to provide the most amount of light output in the least amount of space. Spiral light bulbs are typically used to replace incandescent light bulbs and can be used virtually anywhere, including residential, commercial, retail, hospitality, and restaurant applications.

lk_shape_bt BT – Blown Tube or Bulbous Tube light bulbs

The blown tube light bulb is a T light bulb that has had the glass blown in the middle so that it appears to have a bubble in the middle of the tube. BT halogen light bulbs can be used to replace incandescent light bulbs. High-intensity discharge light bulbs come in BT28, BT37, and BT56. These are used in sports arenas, car dealerships, canopy lighting, and industrial applications.

lk_shape_ed ED – Elliptical Dome light bulbs

ED light bulbs have an elliptical shape to house the arc tube of a high-intensity discharge light bulb. ED light bulbs are used in sports arenas, high bay industrial lighting, parking lots and garages, and car dealerships. Typical sizes include ED17, ED18, ED23.5, ED28, and ED37.

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