# LED Lighting - Rules of Thumb?



## Nature Man (Nov 14, 2021)

Are there any rules of thumb on how many LED lights should be installed per square foot of shop space? Guess it is probably based on lumens, but I don't have the beginning of a clue as to how many I should buy for the workshop I am going to build. Thanks! Chuck


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## Arn213 (Nov 14, 2021)

Nature Man said:


> Are there any rules of thumb on how many LED lights should be installed per square foot of shop space? Guess it is probably based on lumens, but I don't have the beginning of a clue as to how many I should buy for the workshop I am going to build. Thanks! Chuck



1 foot candle = 10.76 lumens.
A workshop requires 30-75 foot candles or 130-150 lumens per square foot. You need general ambient lighting and task lighting. You should compute for more output than less.

It would be good if you had a floor plan layout, reflective ceiling plan/lighting plan as well as electrical plan.

Mike @Mike Hill should be able to add more info. as well as others.

Reactions: Thank You! 1


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## trc65 (Nov 14, 2021)

Here are a couple simple calculators you can use to give you a starting point. A few simple inputs and you can get some good estimates. 









Simple Lighting Layout Estimator | Current - GLI Brands







www.gecurrent.com

Reactions: Thank You! 1


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## Tony (Nov 14, 2021)

I would use the above tools to figure out what it says you should have, then add a couple more to that number Chuck.

Reactions: Thank You! 1 | Agree 1


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## eaglea1 (Nov 14, 2021)

When I was still wiring for a living, we always use the formula of 3 watts per sq. foot., but that was for incandescent.

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## Wildthings (Nov 14, 2021)

I say if you don't have to wear sunglasses you don't have enough

Reactions: Like 2 | Agree 2 | Funny 4


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## Sprung (Nov 14, 2021)

My workshop space is our two car garage. 21' x 22.5' - 472.5 SF. I have about 100,000 lumens of LED lighting installed in there. It is a very well lit space and I find it a great amount of light for the space. It does equate out to about 210 lumens/square foot - certainly a good bump above the numbers Arn gave above - but I love it. This is the first shop space I've had with a truly great amount of lighting and I don't regret it one bit.

Reactions: Like 4


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## Mike Hill (Nov 15, 2021)

Lumens and watts almost mean nothing to what you are asking. And to make matters worse - many fixures use Lux or watt equivalents for their marketing to the unawares - whatever those are! A lux is an illumunation rate of one footcandle per square meter - but is a useless datum, unless you know what the lux is at say 10' from the light source. What you are asking about is how many footcandles (and by relationship - 'the lux") is needed to light your working surface. That is a function of how strong your light is (Lumens is one measure), how the light is diffused (if it is) and the distance from the light source you want to be "well-lit" (remember your physics class and the Inverse law of light -brightness of a source of light is a function of the inverse square of its distance - or something like that) . Plus there are generally two or three types of lighting - task lighting (light locally focused on the task being performed - it lights nothing else , overall lighting (most lighting you will see and it gets dispersed and diffused at many different angles and lights up the entire space). The third I would call downlighting (often are the recessed can lights in a ceiling - they are bright, but not diffused so do a good job of lighting the floor or anything the light falls on, but does not light up the space). First I would decide against overall lights to do everything. They would generally be in the center of the space and cast bunches of shadows especially since most tools are against the wall and your body is between the tool and the light source. I would probably refrain from using any canlights (spotlights) as there are better ways. I'd probably decide to use overall lighting strongly enhanced with more lights above the work stations - say above a lathe, a saw, a workbench, etc.. This could be in the form of adjustable position task lighting or another hanging fixture above the station.

First decide how many foot candles you want at a general illumination (10 to 30 ain't a bad choice) and how many footcandle you want at your task - (generally the finer the task the more - so generally between 50 to 200 - with 100 not a bad choice and bright). Each of the light fixtures you might use should have a chart/graph that shows how many footcandles that particular fixture can provide for a horizontal surface at a specific distance from the light. Generally, the closer the light the more footcandles. i.e. if at a saw station - you want 100 fc at your working height of say 3' from the floor. Your ceiling is 9' - so you want to have a fixture or combination of fixtures that put out enough light that produces 100 fc 6' from the light (9' less 3'). You could have a powerful 4500 lumen light fixture, but if it is in a 20' ceiling and if the work station is 10' horizontally from the light, and the light fixure does not diffuse, there might not be many fc available at your task. It doesn't matter, if incandescent, fluorescent, halogen, hi-pressure sodium, or LED - it all acts the same. You could decide to light up your wholes pace to an average of 100 fc or greater at 3' above the floor, but why go to the expense of lighting the NE corner where your hot water heater resides or the trash can to the same fc as where you do your woodturning? 

Then you also have to decide what temperature kelvin you want the light. There is not one right, but one you like or could be some are better for what you are doing. Some kelvins are are arguably better for dealing with colors than others. Then you also want to decided if you want diffuse light or focused. Lesser amount of sharp shadows with diffuse than focused.

I have a very small shop - 10x18 or something like that. I decided on a fixture in the middle of the space for overall - then hung smaller LED strips over my lathe (s), bandsaw, workbench. I will also have one over my sharpeners when I get them sited permanently. I really don't know the fc - but they are sufficient for what I do. On some really fine stuff, such as my faceting machine and where I will engrave - I also have task lights.

Reactions: Like 1 | Great Post 3 | Informative 2


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## woodtickgreg (Nov 15, 2021)

I'm very scientific in my approach. If an area is dim I put a light there, lol. Im going to add one over my table saw and another over my big lathe. I'm switching over to all 4' 2 row led's in my shop. They claim they are 5,000 lumen and they are daylight white. For as little energy they use you can really add more lights as needed and still save on energy cost.

Reactions: Thank You! 1 | Agree 1


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## Arn213 (Nov 15, 2021)

Well done Lil Mikey @Mike Hill ! Going to add to his detailed info. as these other details are often over looked and it can make or break a space.

Mike already mentioned that ceiling height will affect your beam spread light coverage. But other elements will affect lighting such as fenestrations like glass walls, windows, skylights or any opening from the outside will affect your lightning.
Room orientation is also affected if natural light is present and used in tandem with artificial lighting.

Lighting and lamp color temperature also affects paint color too (and their types of finish from matte to high gloss). Lighter color have higher reflectance color compare to darker shades of a given hue. Types of lamps have kelvin temperature measurements for color output that ranges from 1500k-7000k plus. It ranges from warm white to cool white. LED lighting has different color temperature as well that is either warm to cool white. There is a basic rule in paint color and lamp temperature color. If you use a white with a tint of warm color (red, orange, yellow) or cool colors (green, blues, indigo, violet) you should match the color of the paint with the proper lamp temperature so that it it is enhanced and not diminished. A word from your “Inferior Designer”. Lol.

Reactions: Thank You! 1


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## 2feathers Creative Making (Nov 15, 2021)

Nature Man said:


> Are there any rules of thumb on how many LED lights should be installed per square foot of shop space? Guess it is probably based on lumens, but I don't have the beginning of a clue as to how many I should buy for the workshop I am going to build. Thanks! Chuck


I can't give a rule of thumb, but if you are finishing your projects in the same area, you may want to consider a second set of lights spread out between the others, that are switched separately and only used when finishing. They only need to be in the area you are finishing in. Also, I have had good feedback on lights mounted on the sidewall in the finishing area. Ours are located about a foot down off the ceiling in the finishing/ paint room at work.

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## FLQuacker (Nov 15, 2021)

Arn213 said:


> fenestrations


Lot of info...but this was the word of the day!

Reactions: Agree 2


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## Mike Hill (Nov 17, 2021)

FLQuacker said:


> Lot of info...but this was the word of the day!


Awwww - you're gonna give him a big head!

Reactions: Funny 2


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## Mike Hill (Nov 23, 2021)

FLQuacker said:


> Lot of info...but this was the word of the day!


Plus fenestration by definition has to be about exteriors - and he don't know nuthin about exteriors - only interiors!!!

Reactions: Funny 1


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## Nature Man (May 14, 2022)

Above discussion was very helpful. Now to specifics. Square footage is 1200’, 40’x30’. Ceiling height is 12’ at peak. Metal building, will be spray foamed on inside. Two windows on one of the 40’ sides. At this point I am trying to calculate the number of fixtures needed for general purpose lighting, understanding that I will need task lighting in addition to this, which I will attend to later. Based on other lighting discussions, sounds like avoiding “cheap” LEDs is advisable. I’m sure that lighting placement on the ceiling is also important, so any hints on that would be appreciated. Chuck


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## woodtickgreg (May 14, 2022)

Nature Man said:


> Above discussion was very helpful. Now to specifics. Square footage is 1200’, 40’x30’. Ceiling height is 12’ at peak. Metal building, will be spray foamed on inside. Two windows on one of the 40’ sides. At this point I am trying to calculate the number of fixtures needed for general purpose lighting, understanding that I will need task lighting in addition to this, which I will attend to later. Based on other lighting discussions, sounds like avoiding “cheap” LEDs is advisable. I’m sure that lighting placement on the ceiling is also important, so any hints on that would be appreciated. Chuck


High bay lighting is a little different that what I have in my shop or what most people use in their shops. High bay lights are a little different. Or you cold just hang regular lights lower on chains, but i dont know if i would like that. I know even in my basement shop I had dark areas after most of the lights where hung, but at $20 a fixture I just put another one up where it was needed. Like over my table saw and workbench. Keep in mind my ceiling height is about 7 foot.
I would Google High bay lights to see what the differences and requirements are.

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## Mike Hill (May 16, 2022)

I'm far from an electrical engineer or even a light fixture salesperson, but have had to deal with a number of different types of lighting in my career. What you are essentially looking for is the number of footcandles of light falling onto your work surface. A footcandle (fc) is simply a standardized measure of the amount of light that falls on a surface and is measured by light meters. There are three different types of lighting strategy - no matter what type of bulbs or fixture you use - (i'll use terms that us troglodytes can understand) overall, task, and some combination of the aforementioned. Overall gives an "overall" brightness to the area. Task is focused on specific areas you need abundant non-shaded light. Combination is combination - duh. Usually a less bright overall, but with focused task lighting where you need it. For a wood shop with no task lighting - I've seen recommended about 75 to 100 fcs. With task lighting 50 to 75 fcs or lower. So what does that mean - You need to select a fixture or fixtures so that a specific light distribution curve for that/those fixtures can be used. The distance from your ceiling (or level of your light fixture) down to what you want illuminated - (work level) is highly important. Remember those Physics courses and that pesky Inverse Square Law? Also how distant from one another the fixtures are and their layout. Now, you need to input that data into software that will make a bunch of calcs and give you the fc's that result. Google Free Lighting Layout Tools or software. 

Or - you can use a rule of thumb method. - 

I've seen figures of 75 lumens per sf recommended for shops - you might google to be sure. Multiply the sf of your shop by 75 to get the number of lumens needed. Then divide the number of the lumen output of your chosen fixture into the lumens needed to obtain the number of fixtures needed. You will need enough so that the light patterns overlap somewhat. If you have a low ceiling it might be better to select a larger number of smaller fixtures as they won't have enough distance to spread. 

Perhaps as important as amount of fc's is the location of the lighting. If all your work stations are along a wall, but you want to put all the fixtures down the middle of the shop, your body will be between your work surface and the light source and casting a shadow on your work.

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