What is Lumens, Watts, Kelvins on LED Lights?

With the advent of LED lights, I’m often asked about the terminology found on packaging and light globes in regards to LED lighting. What do all those numbers and letters on the light globe or light fitting mean? A little more technical than my usual articles but hopefully it will help with choosing your light fitting or globe. I’ll highlight the three most useful terms to know; Lumens, Kelvins and Watts.

Lumens (lm)

Lumens is the total amount of visible light given off by the globe or light fitting. It is the brightness of the globe. Therefore the higher the lumens, the brighter the light. The lower the lumens, the dimmer the light.

You will find this commonly printed on light fittings. Shown as a number ie 800lm (800 Lumens). While in the past we chose light fittings based on wattage, with LED’s we now select on Lumens, consequently it may take a little getting used to! As an example, the old common 60W light globe gave off about 800 Lumens.

Kelvins (K)

Kelvin is a number unit that is used to describe the colour temperature of a light. You may have heard of lights referred to as warm or cool. Lights in the 2700-3000K range are yellower and considered to be warm, sometimes called Warm White (WW). Warm lighting is often seen as soft and relaxing and used in bedrooms and living rooms. Lighting around the 4000K range is called Cool White (CW), the light colour being more blue/green and appearing brighter to the eye. This light type can be used in kitchens and bathrooms. 5000-6000K is known as Daylight (DL), and noticeably bluer and brighter than the warmer lights. Often used in meat display cabinets and in retail.

Watts (W)

Watts are how much power a light uses and the way we used to choose our old incandescent light globes. Hence, we knew approximately how much light a 25W (lower light output) or 60W (higher light output) light globe put out. With LED lights we now have to refer to the Lumen output as a gauge for how much light the light fitting will put out. While wattage may be shown on the light fitting, it is only telling you how much power the fitting will use and as a result not a very good indicator of its light output. Some light fitting packaging will have a conversion so you can see what the Lumen output is close to in the old wattage terms, but isn’t exact.