Fluorescent Tube Color Temperature: Codes, Kelvin Values and LED Equivalents
Fluorescent tube colour temperatures explained: what codes like 830, 840 and 865 mean, warm white, cool white and daylight in kelvin, CRI, and how to match LED tubes when replacing fluorescents.
Key points
- Fluorescent tubes are sold in colour temperatures from about 2700 K to 6500 K, marked by a three-digit code such as 840.
- The first digit of the code is the CRI band (8 = CRI 80–89), the last two are the kelvin value divided by 100 (40 = 4000 K).
- Offices, schools and shops usually use 4000 K; warehouses and workshops often 5000–6500 K; homes and hotels 2700–3000 K.
- When replacing fluorescents with LED, match the code (for example 840) to keep the same look across a room.
Fluorescent tubes come in several shades of white, and mixing them in one room looks untidy. Whether you are buying replacement tubes or switching to LED, it helps to understand the colour codes printed on the tube. This guide explains them.
What colour temperature means
Colour temperature, measured in kelvin (K), describes how warm or cool white light looks. Low values look yellowish and warm; high values look bluish and cool. For a full explanation with examples, see the colour temperature chart.
Common fluorescent colour temperatures
| Name used on packaging | Kelvin | Typical use |
|---|---|---|
| Warm white | 2700–3000 K | Homes, hotels, restaurants |
| White / neutral | 3500 K | Shops, some offices |
| Cool white | 4000–4100 K | Offices, schools, hospitals, retail |
| Daylight | 5000 K | Workshops, showrooms, colour inspection |
| Cool daylight | 6500 K | Warehouses, garages, some factories |
The names are not standardised; one brand’s “cool white” can be another’s “white”. The kelvin value and code are more reliable.
Reading the three-digit code
Most fluorescent tubes carry a code such as 830, 840, 865 or 940. The code has two parts:
- First digit: the colour rendering index (CRI) band. 7 means CRI 70–79, 8 means 80–89, 9 means 90 or above.
- Last two digits: the colour temperature divided by 100. 30 means 3000 K, 40 means 4000 K, 65 means 6500 K.
So:
- 827: CRI 80+, 2700 K, warm white
- 830: CRI 80+, 3000 K, warm white
- 835: CRI 80+, 3500 K, white
- 840: CRI 80+, 4000 K, cool white
- 850: CRI 80+, 5000 K, daylight
- 865: CRI 80+, 6500 K, cool daylight
- 940 / 950: CRI 90+, 4000 K or 5000 K, for colour-critical tasks
Older tubes, such as halophosphate types, often carried names like “33” or “29” instead, and had lower CRI around 60–70. Tri-phosphor tubes with codes in the 800s render colours much better.
Colour rendering (CRI)
CRI measures how naturally colours look under a light, out of 100. Tubes in the 800 series (CRI 80+) suit most offices, schools and shops. The 900 series (CRI 90+) is used for print rooms, art studios, hospitals and colour matching. Older low-CRI tubes make skin and products look dull.
Which colour temperature for which space?
Offices and classrooms: 4000 K (840) is the most common. It looks clean and neutral and suits screens and paperwork. Our LED classroom lighting uses 4000 K as standard for this reason.
Shops: 3000–4000 K depending on the products; warm for clothing and homeware, neutral or cool for electronics and supermarkets.
Hospitals and clinics: 4000 K, with higher CRI in examination areas.
Warehouses, workshops and garages: 5000–6500 K is often chosen for an alert, bright look, though 4000–5000 K is easier on the eyes for long shifts.
Homes, hotels and restaurants: 2700–3000 K for a relaxed atmosphere.
Why tubes in one room look different
Several things make tubes in the same space look mismatched:
- Tubes of different codes fitted over the years
- Tubes of different brands with the same code but slightly different tints
- Old tubes whose colour has shifted with age
- Different diffusers or reflectors in the fittings
When relamping, replace all tubes in a room at once with the same code and brand.
Matching LED tubes to fluorescents
LED tubes are sold in the same colour temperatures. To keep a consistent look:
| Fluorescent code | LED tube to choose |
|---|---|
| 830 | 3000 K, CRI 80+ |
| 835 | 3500 K, CRI 80+ |
| 840 | 4000 K, CRI 80+ |
| 850 | 5000 K, CRI 80+ |
| 865 | 6000–6500 K, CRI 80+ |
LED light can look slightly cooler or brighter than fluorescent at the same nominal value, because LEDs often give more useful light downward and do not dim with age as quickly. If a room is partly converted, finish the conversion within the room rather than mixing LED and fluorescent.
For the conversion itself, including ballast-compatible, ballast-bypass and fixture replacement options, see LED fluorescent tube replacement. Our LED T8 tube is available in common colour temperatures.
Should you switch to a different colour temperature?
Replacement is a good moment to reconsider. Many offices fitted with 6500 K tubes in the past find 4000 K more comfortable. Many warehouses lit at 4000 K find 5000 K looks brighter for the same lumens. Try a few sample fittings before changing a whole building.
Fluorescent tubes are being phased out
Many countries are phasing out fluorescent lamps because of their mercury content and lower efficiency. In the EU, most common T8 and T5 tubes have been withdrawn from the market. Elsewhere, supplies are shrinking and prices rising. Planning a move to LED now avoids being caught without spares. The LED retrofit savings calculator estimates the energy savings.
A quick way to check what you have
If the code has worn off, compare the tube with a known sample under the same fitting, or use a phone app with a colour meter for a rough reading. Photograph the end cap of a new tube before fitting it, and keep a note of the code used in each area. Facilities teams that keep a simple record of codes and brands per floor avoid the patchwork look that builds up over years of spot replacement, and they can order LED replacements in one go when the time comes.
Disposal
Fluorescent tubes contain a small amount of mercury and must not go in normal waste. Take them to a recycling point or use a licensed waste contractor. LED tubes are electronic waste and should also be recycled.
Replacing whole fittings
Where old fittings are tired, replacing them with LED panels or troffers may be better than changing tubes. See our guides to LED flat panel lights and LED troffer lights.
Sources
Frequently asked questions
What colour temperature are fluorescent tubes?
Common fluorescent tubes are 2700 K or 3000 K (warm white), 3500 K (white), 4000 K (cool white), 5000 K and 6500 K (daylight). The colour is shown on the tube as a code like 830, 840 or 865.
What does 840 mean on a fluorescent tube?
840 means a colour rendering index in the 80s and a colour temperature of 4000 K, often called cool white. 830 is 3000 K and 865 is 6500 K, both with CRI in the 80s.
What LED colour temperature replaces a cool white fluorescent tube?
Choose a 4000 K LED tube to match a cool white 840 fluorescent. For daylight 865 tubes, choose 6000–6500 K; for warm white 830, choose 3000 K.