LED lighting explained: lumens, watts, Kelvin, CRI, beam angle and IP rating

LED lighting becomes much easier to compare once each number is given one job. Lumens describe how much light is produced, watts describe electrical input, Kelvin describes the colour of white light, CRI describes how naturally colours appear, beam angle describes how widely the light spreads, and the IP rating describes protection against solids and water. A good choice considers all six—not just the biggest number on the box.

Start with the result you need

Before comparing specifications, define the task. Are you lighting a dining table, a warehouse aisle, a driveway, a desk, or a building façade? The same 1,000 lumens can feel very different when spread across a room or concentrated into a narrow beam.

For replacement bulbs, also check the base, physical dimensions, voltage and whether the fitting is enclosed or dimmable. For fixed luminaires, check the installation location, mounting instructions and protection class. Specifications are useful only when the product is suitable for the actual fitting and environment.

Lumens: how much visible light the product provides

Lumens (lm) measure luminous flux: the total amount of visible light emitted. Use lumens as the first comparison when the question is “How bright is it?” Do not assume that a higher wattage automatically means more light.

Two products with the same lumen output may still look different. A narrow beam can create a bright pool or long throw, while a wide beam distributes the same light over a larger area. Diffusers, mounting height, wall colours and room shape also affect the result.

Practical rule: compare lumens for overall output, then check beam angle and installation height to understand where that light will go.

Watts and luminous efficacy: input is not output

Watts (W) measure electrical power. With LED products, watts tell you about energy use, not brightness by themselves. Luminous efficacy, expressed as lumens per watt (lm/W), relates the two:

Luminous efficacy = lumens ÷ watts.

For example, a 12 W luminaire producing 1,200 lm has a nominal efficacy of 100 lm/W. That does not automatically make it the best choice: colour quality, driver quality, thermal management, glare and durability still matter. Use lm/W to compare efficiency between products intended for a similar task.

Kelvin: choosing the colour of white light

Correlated colour temperature (CCT), measured in kelvins (K), describes whether white light appears warm, neutral or cool. It does not measure heat or brightness.

• 2700–3000 K: warm white. Common in homes, hospitality spaces and relaxed exterior areas.
• Around 4000 K: neutral white. A versatile choice for kitchens, offices, workshops, entrances and many commercial spaces.
• 5000–6500 K: cool or daylight-like white. Often chosen for task visibility, security areas and some industrial uses, but it can feel harsh in restful rooms.

Colour temperature is a design choice, not a quality ranking. Match it to the task and neighbouring light sources. Mixing very different colour temperatures in one sightline can make a finished installation look accidental.

CRI: how naturally colours appear

The colour rendering index (CRI or Ra) indicates how faithfully a light source reveals colours compared with a reference source. A value above 80 is common for general lighting. Higher colour fidelity can be important for retail displays, food preparation, painting, inspection work and any space where colour decisions matter.

CRI should not be read alone. Two products with the same headline CRI can render individual colours differently, and colour temperature also changes how a space feels. For demanding professional work, consult the full technical data rather than relying on one front-of-pack value.

Beam angle: focused light or broad coverage

Beam angle describes how widely light is distributed. A narrow beam is useful for accent lighting, long-range visibility and highlighting a defined object. A wide beam is better for general room lighting, close work and broad outdoor coverage.

Mounting height changes the illuminated area. A wide beam mounted low can cause glare; a narrow beam mounted high may leave dark zones. For projects with several luminaires, spacing and photometric data matter more than a single beam-angle number.

IP ratings: read both digits

An IP code has two digits. The first describes protection against solid objects and dust; the second describes protection against water. A higher number in one position does not compensate for a low number in the other.

• IP20: basic indoor protection; not intended for wet or dusty locations.
• IP44: protection against solid objects over 1 mm and splashing water; suitability still depends on the installation zone and product instructions.
• IP65: dust-tight and protected against water jets. It does not mean the product can be submerged.
• IP67 or IP68: includes immersion protection under specified conditions; always check the manufacturer’s exact limits.

Outdoor suitability involves more than IP. Check operating temperature, UV exposure, drainage, cable entries, impact risk and the installation instructions. A product can carry a strong IP rating and still be unsuitable if mounted incorrectly or used outside its specified conditions.

How to compare two LED products

1. Confirm the product type, voltage, base or mounting method.
2. Compare lumens for the required light output.
3. Check beam angle and mounting height for coverage.
4. Choose a colour temperature suited to the room or task.
5. Check CRI where colour quality matters.
6. Compare watts and lm/W between otherwise suitable options.
7. Verify IP, operating temperature and installation limits for the environment.

Useful Nordeks starting points

Browse LED lighting for the wider range, LED bulbs for replaceable light sources, and floodlights for broad task and outdoor illumination. Filter by the job first, then compare the specifications that actually affect that job.

Safety note

Disconnect power before installation. Fixed mains-voltage luminaires and alterations to electrical wiring should be installed by a competent electrician in accordance with the product instructions and applicable requirements. Never select a product for a wet or outdoor location from appearance alone.

Official technical references

• VIDEX LED catalogue 2026
• VIDEX 12 W adjustable-CCT wall light specification—a documented example combining 1,200 lm, 3000/4000/6500 K, CRI > 80, a 120° beam and IP65.