HOW TO CHOOSE AN FLUORESCENT BULB Click to view bigger version

Most elements of a fluorescent light source cannot be changed without first changing your fixture or internal ballast. The wattage, length, shape and base type of fluorescent bulb are set by the fixture characteristics. You pretty much need to match exactly what you have and should have the bulb model number in hand when ordering:

How to interrupt a common fluorescent ordering code F32T8/741/ECO
(F) Fluorescent (32) Watts (T) Tublar (8) Diameter in eights of an inch 8/8 or 1” (7) CRI (41) Color Temp (ECO) Brand Information or other output

(F) Fluorescent - your bulb is obviously a fluroescent
(32) Watts - This one uses 32 watts. This number can range anywhere from 5 to 120 watt.
(T) Tublar - your bulb is a straight tube not a U-shape or C-circle shape.
(8) Diameter in eights of an inch 8/8 or 1” . This bulb is a T8. Other common diameters are thicker T12 and skinnier T5
(7) CRI - Color rendering of lamp - see below.
(41) Color Temp - Color of light itself - usually either 27-warm yellowish, 41-cool white, 51- daylight bright
(ECO) Brand Information or other output such as low mercury or high output designations.

These factors should be considered when selecting a fluorescent lamp.
  • SIZE


When considering light output, wattage is something to keep in mind. Wattage is not an indicator of lamp brightness. Wattage measures energy consumed by the lamp and actual the Light output is measured in lumens or units of luminous flux.


CRI is a lamps ability to render an objects true color based on a scale of 100, with a 100 being a incandescent lamp.
Fluorescents with a CRI of 70 and under are typically in low quality lamps. Colors in the room will appear dull and washed out.
Fluorescents with a CRI of 70-79 are appropriate in commercial applications.
Fluorescents with a CRI of 80-89 are appropriate in commercial and residential applications.
Fluorescents with a CRI of 90-99 are appropriate in high end retail or graphic businesses where true color is important.


CCT is a numerical measurement of the color appearance of a light source measured in degrees Kelvin within a range of 2700K to 6500K. 2700K being the warmest closest to yellow and 6500 being the coolest and closest to sunlight.

  • You have many sizes to choose from when selecting a fluorescent lamp, common sizes are T12, T8, and T5. The T stands for tubular and the number stands for diameter in eights of an inch.
  • T12 are the least efficient tube. They have a high manufacturing cost and are used in rapid start circuits, and ballast systems.
  • T8 are common in commercial and residential settings and are more efficient than T12’s. They have a long life, wide range of color temperatures, low cost, and high output versions are available.
  • There are two Types of T5 tubes. North American T5 tubes are preheat lamp and requires starters and ballast. European T5 is 2 in shorter than North American and is equal light output to a T8. High output versions are available.


You have many shapes to consider when buying a fluorescent lamp. Fluorescents often come in linear shaped tubes, bent shaped U-tubes, and circline shaped.


Most common fluorescent base is a medium Bi-pin. Other bases include mini bi-pin, recessed DC, single bi-pin, 4pin, and a 2Gx13.