Electricity is used as one of the main sources for producing light. We use different rating bulbs for lightning. And we know how much the watt rating of a bulb is.
The more the watt the more brightness will the bulb produce. In this article, we will study the term “Lumen” and will discuss the conversion of Lumen to watts.
Should I use Lumen or Watt to describe a lamp?
We can define the lumen in a very simple way “the measurement of visible light from a light source such as a bulb or Lamp etc.” The lumen is denoted by lm. The brighter the light the higher the value of the lumen.
Most people describe light bulbs and lamps using watts. This is not the true way as the watt is the electrical energy that the lamp consumes.
Lighting lamps output is not in watts but it is in the lumen. This is why it is important when purchasing a new lighting lamp or spot light to check the lumen of the lamp.
Some poor-quality lamps consume high power in watts and don’t produce much brightness.
lumen to watt formula
We can measure the efficiency of lighting products such as bulbs, lamps, etc. from the lumen to watts relationship. Therefore, the efficiency of a bulb or lamp will be the amount of total output light (in Lumen) divided by the power used (in watts). So using this relation we can decide and measure the efficiency of lighting products. Let’s take an example.
Assume there are two lighting products “A “and “B”. Light A offers a light output of 4000 Lumen for 20 Watts of power. And Light B offers a Light output of 5000lumens for 40 watts of power.
Now according to the lumen-to-watts relation, we can determine the efficiency of each product.
- For Product A, Lumen per watt relation= 4000 lm / 20 watt
- The efficiency of Product A =200 Lm/ W
- For Product B, Lumen per watt relation= 5000 lm / 40 watt
- The efficiency of Product A =125 Lm/ W
So from the formula, we decide that product “A” is the best choice to use not product “B”.
Does more lumen mean brighter?
Yes. More lumen means, it will be lighter (brighter). Lumen is the measure of visible light.
It is represented as lm. Lumen is defined as the unit of luminous flux. Luminous flux is the quantitative measure of brightness.
Lumen being the measurement of visible light shows how much energy the light is emitting from the source. Let us see how many lumens these watt-rated devices have.
A 25W lamp will have 230-270 lumen. A 35W spotlight has 250-280 lumen while a lamp of the same wattage rating has 390 to 410 lumen.
440 to 460 lumen are delivered by a 40W lamp. A 50W spotlight is able to deliver 300-400 lumen. 60-, 75-, and 100-watt lamps are able to brighten the surroundings with 800-850, 1000-1100, and 1500-1600 lumen.
The brightness that is measured in this way is directed in a spherical direction. The quality of using lumen measurement is that it does not change with distance. Let us suppose we measure the brightness of the bulb at 2 meters and record its value.
Then again, we measure the brightness at a distance of 4 meters from the source and record this value.
When we compare these values, the value of light intensity at 4 meters will be half the value at 2 meters. But the area at 4 meters will be 2 times the area at 2 meters.
Does high lumen equal excellent viewing quality?
No, not always. High lumen is the measure of brightness. High lumen does not have better colors and vividness.
Let us discuss this matter with respect to a projector. We adjust the lighting (brightness) and the projection size for a particular length of the room by the degree of brightness and ratio of contrast.
The projector image brightness output sets the brightness of the bulb that is actually measured in lumen.
While the color dynamics of the image depend upon the value of contrast. For better quality at a shorter distance, we need a better value of contrast.
A better value of contrast can be found by the ratio of extremes of contrast. Lumen is counted as an important factor at larger distances.
Because the crispiness of the image (knowing the limit of an object being shown in the image) is attained only if there is enough brightness for each object to show itself.
So, from the above discussion, we can say that, yes, lumen affects the quality of the image but only when we are a little too far from the image projected from the projector.
So, just brightening the image will not help you get a better-quality picture, it will just cost you more wattage and a relatively expensive bulb.
Which is brighter, lumen or candle power?
The candle power of Candela is brighter than the lumen. 1 Candela is 12.57 times brighter than the lumen. But we must keep in mind that these units do not indicate the same thing.
We know that lumen is the measurement of the total light emitted from a light source. But one the other hand, candela is the measure of the brightest part of the light or we can say the luminous intensity is candela. Let us understand it from an example.
Suppose, it is nighttime and you’re in a jungle. You have a torch that has a very good lumen rating. You turn it on and everything around you is illuminated.
But your friend has a torch with a high rating of candle power. He takes it out and turns it on. But nothing around him is illuminated but the light from the light source is just directed towards a single point and is really bright. This is the difference between candle power and lumen.
Lumen provides you with a light that is helpful in doing work. But the lumen does not tell us where the light will go. Lumen can be trusted the providing light in the places like houses, buildings, and showrooms.
Where the main purpose of the light is to shine. Candela is important in the things like automotive and directed lights. We cannot use things rated in the lumen and the things rated in candela interchangeably.
Say we use a lumen-rated bulb in a vehicle. It will glow in all directions giving out much more light than needed.
We know there are certain regulations we have to follow when driving with the lights on. Too much brightness can also break these regulations. So, choose your lamps and lights wisely.
How to convert LED lumen to ANSI lumen?
We use a formula to convert LED lumen to ANSI lumen. Mathematically,
ANSI lumen= (LED lumen)/2.4 or
LED lumen = 2.4 ANSI lumen.
We can say that the ANSI lumen is greater than the LED lumen. Because for the same brightness, the value of a lumen is 2.4 times the ANSI lumen.
Let’s see how it works. For example, we have a 480-lumen lamp. The ANSI lumen of this bulb will be equal to 200. Some simple lumen are converted to ANSI lumen for you in this table.
| ANSI Lumen | Lumen |
| 200 | 480 |
| 300 | 720 |
| 800 | 1920 |
| 900 | 2160 |
Can a flashlight really be 90,000 lumens?
Yes, a flashlight can be 90k lumen. It is not a very surprising fact that a flashlight can be a 90k lumen delivering device because, after all, we are applying science.
It is a very common practice to use these kinds of flashlights in many countries. But obviously, the size is not like a torch but a little bigger than a DSLR camera.
A common 90k lumen flashlight has a range of 500 meters. It is like if you are in a jungle and you light up this flashlight, everything around you will glow as it glows in the day.
Yes, you can question the idea that leads to designing such a huge light but according to physics and electricity, it is perfectly alright to design a light like that.
Normally, hikers, hunters, and people who like to adventure buy these kinds of battery-powered flashlights. An 800mAh batter that can deliver 90k lumen can work for 4 to 6 hours.
The battery timings depend upon the conditions of weather, and other factors such as life, etc. This flashlight has can end up to 100,000 hours.
Do more bulbs equal more lumen?
Yes, more bulbs mean more lumen. Lumen adds up in a linear addition manner. It means that if you place 2 bulbs of 100 lumens each in a room, the total lumen delivered will be 200.
But there are some rules you must keep in mind to observe the real effect. Because our eyes won’t be able to differentiate between a source of 100-lumen brightness and a source of 200-lumen brightness.
The reason is that our eyes work on a logarithmic scale rather than a linear scale. The deflections on the linear scale will not be perceived exactly by our eyes. One of the rules is that the bulbs should not be adjacent.
Adjacent placement of bulbs leads to lesser observable light due to the shadowing effect of the adjacent bulb. The other, important, detail that we should keep in mind is not to expect that the brightness in the place, let’s say container, will increase.
Lumen means light intensity in a particular direction. So, to observe the light intensity, measure the total incidence of light.
So, we can say that the lumen does add up; this addition is also due to the adding up of light sources but we, most of the time, are not able to perceive it through our naked eyes.
At how many lumens of light can humans see?
There is no perfect answer to this but engineers, through their observations, have discussed some answers to this question.
Normally, at 0.1 lumens per 1 square meter will shine in the dark. It will not have a sparkle nor will be able to light its surroundings up.
The light source will be like a star in space that exists in the dark sky but its light is not useful. But some other engineers have observed that a small flashlight that delivers only 0.003 lumens can be seen in the dark.
If you light it up and move for like 2-3 meters; after 3 meters you won’t be able to see any light, everywhere it will be just darkness. So, we can say that up to 0.001 lumens, human eyes can detect the light source.
We can call a light-emitting thing a light source if it delivers 680 lumens per watt. Then the light will be observable and it will also be illuminating the things around itself.
How many lumens will be too high for comfort?
For the comfort of the eyes, light intensity should not be more than a specific value. These values depend upon where you are sitting or working.
In the workplace, we need more light. So, if the light is lesser than that value, or even more than that value, our eyes will irritate.
In a workplace, 8000-10,000 lumen will be very efficient light intensity. Similarly, kitchens are one of the most important places.
Kitchens should not have any dark corners and visible shadows on the tables.
A light intensity value of 7000 to 8000 lumen gives very good illumination.
For the comfort of the eyes, in the dining room, a light intensity of 3000-4000 lumen is really appreciated.
Bedrooms normally need 1000 to 2000 lumen for proper lighting. The intensity illumination of hallways is not a critical factor unless it is the main entrance.
Normally, 500-1000 lumen is recommended for hallways.
And for entrances, 2000-3000 lumen is enough to light. Eyes are sensitive and can get hurt from too much brightness.
The values written above are applicable to a standard room, office, dining, and kitchen workspace.
For more precise calculations, try to use the following values. In the hallways, 5-10 lumen per square foot is enough.
70 to 80 lumen are the requirement for our eyes in the working area of the kitchen.
In the dining hall, light lesser than 30 lumens per square foot and more than 40 lumens per square foot is undesirable.
What is the relationship between voltage and lux/lumen?
Voltage is one of the most important factors for the light intensity of a light-emitting source. the Voltage across the terminals of the light source is necessary otherwise the light source will not work.
Increasing the voltage applied to a circuit increases the charge flow through the circuit i.e., the current increases. In short, the power increases as:
P=VI/t [Joules/s]
Normally, light sources such as LEDs and bulbs have a wattage rating. That is an old way to say how powerful a light source it will be.
Nowadays we use lumen to measure light intensity. The watt rating tells us the amount of energy that is being delivered per second to be converted into light energy, in the form of photons, or other forms of energy.
Photon is a smaller unit to measure lumen. But this conversion varies from source to source. Let us understand this way.
A 30-watt halogen bulb is hanging on the ceiling. Now if we increase the power supply, we expect an increase in brightness. But it does not happen. Because the conversion between electric energy and light energy is not the same anymore.
Electric energy is being converted to heat energy and the light energy is constant. If we keep increasing the voltage and the halogen bulb keeps on heating up, it will eventually burst off.
But in certain limits, before bursting off, the bulb/LED does increase the lumen output. If the voltage increases the lumen will increase but it is not a must that the lux will also increase.
Lux is lumen per unit area. If the lumen in a particular unit of area increases, the lux will increase. But if the lumen per unit area does not increase, lux will also not increase.
This happens when the light source is too far away from the unit area under consideration. Mathematically, the formula from lumen to watts:
Pw=Ф v(lm)/η(lm/W)
Where Pwis the power in watts,
Ф v(lm)is the lumen flux in lumen
Andη(lm/W) is the luminous efficacy.
To convert from power in watts to lumen:
Ф v(lm)=Pw.η(lm/W)
Now, to convert from lumen to Lux we have a formula:
Ev=Ф v(lm)/A
Where Ф v(lm)is the luminous flux,
Ev is the Lux, and A is the unit surface area.
We can use the above-written equation interchangeably to convert Lux to Lumen.
