I have replaced an older 100W incandescent light bulb with an led 3000K 1400 lumen light bulb but it seems very bright so I wonder if the lumen output is too high. How can I calculate the correct lumen output needed for my space?

What is an ideal lightbulb temperature for computer room/use? The 3000K led is a lot whiter than the old incandescent, perhaps easier on the eyes but too bright in my case.

Room Diagram: enter image description here

  • 2
    Color temperature and lumens are inherently subjective to personal preference and also subject to a lot of factors (size of space, other light sources such as windows or adjacent rooms, and wall color to name a few). Were you happy with the 100W incandescent bulb light output and color temperature for the space? If so, then I would recommend rephrasing to ask about color temperature and lumens to achieve the same look as a 100W incandescent with an LED bulb. – statueuphemism Apr 15 '17 at 13:13

What you're up against there is color rendering index or CRI. It's also possible you have a mislabeled LED which is not in fact 3000 degrees K.

Both are a problem when buying "bargain" bulbs. Unfortunately there are several "semi-famous names" which you see a lot at your preferred store and dominate the aisles there, which are in fact Cheese cheapies right off the boat. Not to mention any names, they have initials like Ut, LoA or FE.

I buy GE brand which dominate the shelves at my local Target, and they are indistinguisable from incandescents. GE knows a thing or two about light bulbs, having invented them.

  • Not sure about mislabled, the bulb is a Philips 13W LED, 1400 Lumen, 3000K Warm White. Philips seems reputable... This bulb has much more noticeable white in it compared to the 100W incandescent. It's ok and I could get used to it, it just seems a little bright for the space... – Kol12 Apr 16 '17 at 4:18
  • P.S. Phillips website claims their LED's have a CRI of 90%... – Kol12 Apr 16 '17 at 4:20
  • Philips is a top brand IMO. It will be bluer but only slightly, in the way a halogen is slightly bluer than a plain incandescent, When I'm doing work with paper at a desk, I want 2-4k lumens, when working on my desktop PC, 600 lm is fine. Don't want to wash out the screen. – Harper - Reinstate Monica Apr 16 '17 at 4:45
  • I take it the paper work at desk is during the day? Can you explain washing out the screen? 600 is a lot less than the 1400 lumen I have, do you suggest I lower that? – Kol12 Apr 16 '17 at 9:00
  • Washing out is when the light is too bright for looking at the the screen to be comfortable. didnt realize how small the space was. 1400lm is a good work light but I would think you'll want something a lot dimmer for computer use, like 400lm. – Harper - Reinstate Monica Apr 16 '17 at 14:04

"Calculate the correct lumen output" & "ideal lightbulb temperature"

implies a lot more definition to "correct" and "ideal" than seems likely to apply to a matter of individual tastes. For some folks the light in the computer room comes only from the screens, and it goes up from there. There may well be architectural standards, but whether you like the result is going to vary anyway. So:


Try different bulbs until you like one.


Or: Replace switch with (LED-rated) dimmer and adjust to suit. This can actually be tricky as many LED dimmers have minimum loads for stable operation that are more than a single bulb. Also, the LED needs to be "dimmable."


1400 Lumens is pretty bright depending on how far the bulb is from your eyes and between 600 and 1000 Lumens is plenty bright for most applications.

Now the Kelvin ratings these days generally falls into three groups.

  • Warm White 2700K Kelvin
  • Natural White 3000K Kelvin
  • Cool White 3500K Kelvin and up

The Coloring Rending Index, or CRI, is a measure of how well artificial light compares to real light. A CRI of 100% being true light.

A real incandescent flame will emit 2700K Kelvins and has a nice CRI of 100%. Most lower end LEDs on the market are 3000K Kelvins and have a CRI of 80% -- This tends to be more white and less colorful ( especially when dimmed ).

The higher end LEDs are 2700K Kelvin with a CRI between 90-95% -- These tend to be more compatible with existing incandescent giving off that warm white most people are used to.

There are some parabolic "PAR" LEDs on the market that have a CRI of 93% and 2700-3000 Kelvins. These mimic halogen based reflector bulbs without all the heat.

For your application it would be hard to know which bulb would work best as there isn't enough details but hopefully you've learned some things here to shop wisely.

  • I've attached a room diagram. Maybe 1400 lumens is too bright for that area? Maybe it would be better in the bigger area? The bulb is a Phillips 13W, 1400 lumen, 3000K LED with apparently a 90% CRI. Do you think 3000K is suitable in a home computer room? I'm interested in these too, the Phillips Scene Switch: usa.philips.com/c-m-li/choose-a-bulb/sceneswitch They have three different temperature modes, but I'm not sure the ranges would suit me so maybe a dimmer instead. – Kol12 Apr 16 '17 at 5:13
  • Personally I use soft white 2700k in lamps. If feasible I'd use hurricane lamps 24/7. That's just me. – Kris Apr 16 '17 at 13:28
  • These are ceiling bulbs not lamps... I kind of like the little bit of extra white in 3000k but the lumen output I've chosen is too high for this space... I'll either buy a lower lumen bulb or try one of the Phillips Sceneswitch bulbs... – Kol12 Apr 17 '17 at 5:53

Color calibrate your printer and monitor using a device. Then choose the bulb color-temperature so that they match to your eyes.

  • I have my monitor colour calibrated... – Kol12 Apr 16 '17 at 4:19

Tl; dr: choose a bulb (or bulbs) that give you about 30-50 lumens/ft2, and a color temperature of about 4100K

For the lumens output question: The key component missing in your question is the size of your room. What you want to consider is not total lumen output, but lumens per square foot (or foot-candles). To look at it another way: we put smaller bulbs in our cloests, and bigger bulbs in our living rooms. Closets tend to be small, and living roombs bigger.

You can read more in this GSA publication for lighting guidelines for US Government office buildings, or you could get way into the weeds reading through the Handbook of the Illumination Engineering Society.

For the color temperature question: This becomes more personal preference, but is also somewhat dependent on the work you do in your office. If you're just doing general office productivity work, 4100K is a good choice. If you're doing color-correct work (like photo editing, printing, or other visual manipulation), you may want to go even cooler. Keep in mind, too, what surfaces the light is bouncing off of. If you have a cool light bouncing off a warm ceiling, it's going to change the light reflected to your work surface. If you have a white ceiling, the light will remain more or less unchanged.

  • I've attached a room diagram which could help with determining the correct lumen output needed. The diagram scale is not exactly accurate but the measurements are... I just wondered whether a slightly whiter temperature could be easier on the eyes at the computer. The 100W incandescent can be a bit dull, are most 100W incandescent about 2700K? – Kol12 Apr 16 '17 at 4:32
  • P.S. Ceiling is white. Obviously the light is used at night time. – Kol12 Apr 16 '17 at 4:33

We specify "indirect light" (up-light) and 3500k-4100k with dimmers. (By the way, the "white" paint color on the ceiling is important too. )

  • Oh, the indirect light prevents the "bright bulb effect" from shining (glare) on the computer screen. – Lee Sam Apr 15 '17 at 20:19
  • Have white ceilings and light gray walls... – Kol12 Apr 16 '17 at 4:34
  • If the "white" ceiling is yellow-ish or red-ish it will change the tone (color) of the light bulbs. We use pure white. – Lee Sam Apr 16 '17 at 6:02
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    Oh, the wall color doesn't seem to matter so much. The ceiling seems most important because we use up light. (However, we have learned not to use yellow-ish or green-ish colors on the walls in doctors clinics bathrooms, because when patients see themselves in the mirror they think they "think" they feel bad.) – Lee Sam Apr 16 '17 at 6:08
  • I'd like to think my ceilings are pretty white! A fresh coat of paint? No I don't think they're that bad... – Kol12 Apr 16 '17 at 9:03

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