Watt or Lumen

Watt or Lumen?

Before we begin to redefine how we measure light, I would like to wish you a Happy New Year!
I hope 2015 will be a year of Flourishing and Prospering!!!

Up until now we used to indicate the amount of light we needed or wanted by specifying watt.
Based on the old and common incandescent light bulb (40W, 60W, 75W and 100W) – knowing the watt meant you could accurately know the amount of light you would get.

Watt (W)

A watt is a measurement of electrical power, formally equal to the amount of energy in 1 ampere of current flowing at 1 volt.

With modern light bulbs, CFL (Compact Florescent Lamp) and LED (Light Emitting Diode), we find that using watt as an index for strength of light not only no longer works but can also be misleading.

Both CFL and LED need less watt to generate the same amount of light as an incandescent light bulb. This becomes further confusing with LED, as similar types of LED with the same amount of watt output can generate different amounts of light.

To solve the confusion we need to change the way we look at light bulb ratings.
We should look at watt for the amount of energy we are spending but use lumen to indicate how much light the light bulb is generating.


A lumen is a measurement of light directly relevant to human beings. Instead of trying to measure the number of photons or raw radiated energy, the lumen scale describes the amount of light, or brightness, that the human eye perceives. All modern light bulb packaging shows the number of lumens the bulb produces.

In order to work with lumen it is helpful to first know how much lumen the old incandescent light bulbs generate. For this reason I have produced a table below:

Incandescent Light Bulb rated in watt Lumen output

25W 225Lm

40W 415Lm

60W 710Lm

75W 920Lm

100W 1300Lm

When we are looking to buy a light bulb we should first establish how much lumen is needed to properly light up our space. One way to do this is to use the familiar incandescent lamp as a reference. Most of us know which incandescent light bulb is sufficient, thus we can use the table above to find the amount of lumen we should be looking for when sourcing the right modern lamp for us.

Less is more

If in the past more watt meant more light, today we see it is no longer the case.
Further, as we look to save energy (saving electricity and money), the less watt we use the more we save. That is, we want a lamp that is low in watt but is high in lumen.

It is our responsibility to educate our customers.
Remember – we are looking for less watt with the desired amount of lumen.