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How many lights do I need?

Click here for a sample of our light layout package.

Click here for an explanation of understanding layout numbers.

Please note this is for a work area, not just general storage.

Are you "in the dark" about how many lights you need in your building? What type of lights you need? How should you position them? Well, let's "shed some light" on that situation. 

To start, there is no single light setup for every situation. You may see other companies online or on social media giving one size fits all suggestions. (hyperlite, adiding, green light depot, and so on.)  I am many times amazed at how inaccurate many are. Most of their customers are going from a lightless building or poorly lit building to brand new lights. So, they will naturally be impressed. But in general, that fades after time moves on and they see other buildings or move objects in. I have seen many at 50% of what they should be. This isn't a dig on the companies, most are China-based companies with US stock and a couple of US representatives to take phone calls. The vast majority of them have never used their products in real-world situations. Only what theoretically works. That's where we differ. We have extensive real-world experience with how light works in different situations. And we adjust computer models to reflect that. But enough of that, let's get to the numbers,

Ceiling height is the first factor. Taller ceilings need more light to get the light to the ground. Just like a flashlight gets dimmer the further you get away from it. Lumens per square foot (also known as footcandles) is the standard measurement. Another term is Lux which is equal to 10 lumens per square foot. Here are some suggested light levels for different heights:

  • 8' to 12' - 75 to 85 lumens per square foot                                               
  • 12' to 16' - 85 to 95 lumens per square foot                                             
  • 16' to 20' - 95 to 110 lumens per square foot                                           
  • 20' to 24, - 110 to 130 lumens per square foot. 

Click here to see how different ceiling heights change workplane lumen levels.

Once you have determined the light level, the next question is "how many lights do I need?" Well, that depends. Do you have an open empty room? Will there be multiple medium to large-size objects in your space? First off, we will do a little math to figure out the total lumens needed in the building. A starting point is square foot of the space times the light level that fits your ceiling height listed above. So, let's say you have a 60'x80' building 18' tall. We will choose 105 lumens per square foot. 60 x 80 = 4800. 4800 x 105 = 504,000. That is the total amount of lumens you need in your space. 

Now that we know we need 504,000 lumens, we can buy lights, right? Well, not really. You need the right amount of them and what style. Picture this, you have one 500,000 lumen light in your building or 50 10,000 lumen lights. Which option will provide better light? Obviously the second option. Now, this is an extreme example, but it still applies to all buildings. Taller ceilings can use brighter lights with wider spacing and shorter ceilings need dimmer lights with closer spacing. BUT, there's a catch. Taller ceilings in spaces that will have large objects in them need closer light spacing. Such as a farm shop with a combine inside or a manufacturing facility with large machines. If too few lights are installed, large objects can block a larger percentage of the total light resulting in shadowing.

Click here to see how large objects impact light distribution.

Now, to make the final decision. First off, you can email us at "" with your building size/use and we can provide a recommendation. If you don't want to do that, here is a guideline. In general, we do not recommend circular or "UFO" lights below 15 feet. The main reason is they don't give enough light spread. You can just increase the number of them if you want that type, but there are better options. The second reason is a circular light gives off a circular light beam. We are assuming your building is rectangular rather than round so a rectangular light is a better option. Once you get above 15 feet, the light has more opportunity to spread and reflect so the light shape isn't AS important. However, also consider headroom. The circular high bays hang from a hook and will take up almost a foot of clearance in general. The linear high bays can be direct surface mounted and will only take up 2-3 inches of space. Here is a guide to light type and wattage selection:

  • 8' to 12' - linear lights under 110 watts or 15,000 lumens                         
  • 12' to 15' - linear lights under 140 watts or 20,000 lumens                       
  • 15' to 20' - linear or circular lights under 160 watts or 25,000 lumens     
  • 20' to 25' - linear or circular lights under 230 watts or 40,000 lumens. 

So, let's consider the 60x80x18 building we talked about above. We need a total of 504,000 lumens with lights under 25,000 lumens. We could use 21 of the 160w linear high bay lights spaced evenly in the building with the outside rows being half the distance from the sidewall as the remaining row spacing. We can increase or decrease by a couple of lights to make our rows even. If you want the building brighter, use this same layout but go to brighter fixtures. 

Now, you might be saying "it sounds like you are trying to get me to buy more lights so I spend more." Well, we are in business to make money but that isn't the case. If you use the information above on total lumens using less fixtures with more lumens vs more fixtures with less lumens, you will generally find less than a 5% difference in the project cost. In fact, some cases end up being cheaper using more fixtures with a lower output. Here is a general spacing guide for different heights. A general rule of thumb is 1 foot of spacing for every foot of ceiling height. And half that distance from the walls.

  • 8' to 12': No more than 11' spacing. No more than 6' from walls
  • 12' to 16': No more than 15' spacing. No more than 7' from walls
  • 16' to 20': No more than 18' spacing. No more than 9' from walls


As always, feel free to call or email us with any and all questions.

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