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I want to use my garage as a workshop, but it is currently not well lit. How can I estimate how many lumens of lighting fixtures I should buy?

I'm confused about the calculation, but also lighting seems to be a bit subjective. I am rarely annoyed by rooms that are too bright but I often get bothered that they're dim. I don't want to do a bunch of work installing lighting, only to discover that it's too dim for my liking and I need to start over.

What factors are relevant for this?

  • Do I go by lumens or foot-candles?
  • Does size of the garage matter?
  • Does shape of the garage (ie. long vs. square) matter?
  • Does the height of the ceiling matter?
  • Does the color of walls affect it?
  • Does it matter that some lights are omnidirectional (bulbs) while others (strip lights) direct it all downwards?
  • What about the contribution of windows?

From searching on the internet, I basically find that a workshop should be "800-1000 lux" and that you need lum = lux * sqft. However, how can this formula be correct if it doesn't take into account most of the above? What is the correct formula?

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    This needs to be reworked so it asks just one question. Yes, all the factors you bring up could be relevant to your situation, but it's all a matter of opinion how important each is.
    – gnicko
    Commented Sep 19, 2023 at 0:36
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    Not an answer, but in my workroom, I have a set of standard bulb lights to provide general lighting that isn't too bright, but typical room brightness so I can find things as needed. I then have a series of LED strip lights spread evenly across the ceiling that are on a separate switch to provide good even and bright lighting that's a lot brighter when I'm actually working on a project. You might want to consider having multiple lighting circuits to give different levels of light depending on different task needs.
    – Milwrdfan
    Commented Sep 19, 2023 at 2:00
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    "How many lumens do I need for a workshop?" "More. 😀" I have a space with about 1500lm/m² (36W / 5500lm bulbs), and it's... adequate. As to "direction", it may make more sense to look at what fixtures and bulbs are going to be most convenient and/or available.
    – Matthew
    Commented Sep 19, 2023 at 14:58
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    If you are thinking and planning this much you should really think about what activities you will perform and where exactly they will be, where you will stand while performing them and how to reduce shadows. You need much better lighting for EG finish painting, fine electronics work, fine woodworking, than you do for EG storing garden tools. If you just go for overall brightness levels you'll have light in all the wrong places.
    – jay613
    Commented Sep 19, 2023 at 17:56
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    lumens, lux, foot-candles, etc. in this context are essentially relative values. Yes, all those "sub-questions" factor in, but I don't think there's any solid way of predicting how many lumens|lux|foot-candles you're going to need. It's pretty subjective. It's not worth an answer, but if it turns out that your room isn't bright enough, add more light; if it's too bright, cut back a little.
    – gnicko
    Commented Sep 19, 2023 at 19:05

2 Answers 2

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That's lot of decent questions. I'll go much quicker than I would to answer one, but hopefully I give you some starting points.

Do I go by lumens or foot-candles? Go by lux on the work area, aim for 200-500 lux. Lookup the "rule of squares" for info on how to convert a bulb's lumens to an incident lux (1 lumen at 1 meter produces one lux). Lookup a lux chart to get an idea of what you want to go for, level-wise.

Does size of the garage matter? Yes, more area means more lumens will be needed to achieve a given lux. A large area often contains workspaces that demand task lighting as opposed to just ambient/overhead. Don't place light sources when the back of your head will cast a shadow on the area you're looking at or working on.

Does shape of the garage (ie. long vs. square) matter? Not really, it's the distance from the bulb to the surface that matters most.

Does the height of the ceiling matter? Yes, the further away the bulb is from the floor, the brighter it will need to be to light that floor at say, 100 lux, which is a bright minimum, like you ask for.

Does the color of walls affect it? Yes, white walls will increase the ambient lighting level by about 25% compared to dark walls. Bright colors will produce a color hue to the room's lighting that you have to counter act by choosing lights with an opposing color cast on the color wheel, for example warm white against a blue or green wall.

Does it matter that some lights are omnidirectional (bulbs) while others (strip lights) direct it all downwards? Yes and no. Light is light and will bounce around, so adding more of any type of light will tend to make the whole room brighter. Strip lights actually cast in a very wide angle, about 140deg, with about half of the lumens concentrated in a 45deg center cone.

What about the contribution of windows? They are a lot brighter and have a lot cooler color than most light sources during the day, and are dimmer and warmer around dusk/dawn. But it's often cloudy and dark, so design a system that doesn't rely on window light to illuminate the areas you care about.

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  • While white walls may only give 25% better illumination, it's possible to use more reflective material than white paint. But also the apparent effect can be greater anyway as shadows are much less pronounced (so leaning over a workpiece, you're not in your own light nearly as badly if the bench is against a white wall.
    – Chris H
    Commented Sep 19, 2023 at 16:32
  • Thank you for going over all the points. Why do you say that I should go by lux, when I still have to factor in the floor area and ceiling height? Lux measures the intensity of the light source. However, it seems to me like I don't really care about an intense light far away vs. weaker one that's closer for this. Since we really care about total light falling on unit area, doesn't it make sense to set the target in lumens, so that it could compare to workshops of other sizes? Commented Sep 19, 2023 at 17:43
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    Lumens is the intensity (flux) of the light source, not lux. Lux is cross-comparable between rooms, whereas identical lumens will produce different surface lux based on distance and area, and to a small extent, color and texture. Think of a sound analogy: lumens is watts of amplification, lux is sound level db; right by the speaker it's much louder than far away, same with light. At the end of the day, you need enough lumens in a given environment to produce the right amount of lux for the task. Lumens=input, lux=output. 500 lumens yields more lux in a bathroom than a backyard.
    – dandavis
    Commented Sep 19, 2023 at 17:58
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Answer to all the above is "yes", unfortunately. Simplest answers I found are a combination of:

  1. Figure out what I'd do if lighting it adequately with other bulbs, look at how much light those put out in lumens, get equivalent output.

  2. Overkill, then put it on a dimmer so you don't have to run it at full brightness when you don't need to. My living room has a 16-bulb chandelier; I selected the LED bulbs so their total light output would be about equivalent to a 300W incandescent light bulb (which is what I might have picked for that room), then mostly run it dimmed down to 40% when reading, 30% for other tasks.

  3. A serious work area can rarely have too much light. In the basement, I replaced a bunch of two-tube fluorescent fixtures with LED "shop light" fixtures knowing that anything I did was going to be a huge improvement.

Also went to "daylight" spectrum LEDs, (less yellow, more blue), which I think has been a distinct improvement; I'm probably going to drift the rest of the house in that direction over time.

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    Regarding 2, the LEDs are actually quite expensive. I dunno, maybe a retired IBM engineer has a more permissive budget, but I really don't want to pay for a bunch of lights that I'll then keep off because they are too bright. That's why I want to have an estimate so I can figure out how much I need. It's one thing if I have to dim them down to 80-90%, but buying 2-3x more lights than needed seems extreme. Commented Sep 19, 2023 at 20:31
  • Regarding 3, many people in this question and the linked one are saying that my estimate will be "way too bright". And then other people are recommending I have as much as 3x more. So not sure what's going on here. Commented Sep 19, 2023 at 20:32
  • @gomennathan - In that case consider some low-level general illumination combined with some movable "task lights".
    – IronEagle
    Commented Sep 19, 2023 at 23:46
  • @IronEagle Well, the question is not "what types of light should I consider" but "how can I estimate the total illumination I need to provide". Commented Sep 19, 2023 at 23:47
  • I overshot because there are times and tasks for which I want that full brightness, and it was easier and more convenient for me than I stalling additional fixtures in the living room. For the workshop -- roughly 350 square feet, 7' floor to rafters, no ceiling to reflect light -- I just dropped in four $50 LED hanging shop lights and figured I could add more if necessary (it wasn't). How much light is needed depends on the space, what you are trying to do there, and personal tastes. Which is why I suggest starting by figuring out what your current conditions are.
    – keshlam
    Commented Sep 20, 2023 at 3:17

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