Calculating the UFO High Bay Lights You Need for Your Space
Calculating the UFO High Bay Lights You Need for Your Space
Lighting a large commercial or industrial space isn't just about picking a random number of fixtures. To achieve optimal illumination—one that's both efficient and effective—you need to perform a simple but crucial calculation. This process, often referred to as a "lighting layout" or "light plan," ensures you get the right number of lights, positioned correctly, to achieve the desired brightness for your specific application.
Here is a step-by-step guide on how to calculate the UFO high bay lights you need for your space.
Step 1: Determine the Required Foot-Candles
What it is: A foot-candle (fc) is the standard unit of measurement for illuminance, or the amount of light that falls on a surface.1 One foot-candle is equal to one lumen per square foot. The required foot-candle level depends entirely on the activity performed in the space.2
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Scientific Principle: The Illuminating Engineering Society (IES) publishes standards for recommended light levels for different environments. This ensures that the lighting is adequate for visual tasks, enhancing safety and productivity.
Common Foot-Candle Recommendations:
| Application | Recommended Foot-Candle (fc) Range |
| :--- | :--- |
| Warehousing (General) | 20 - 30 fc |
| Manufacturing (General) | 30 - 50 fc |3
| Gymnasiums / Sports Arenas| 50 - 75 fc |
| Retail / Showrooms | 50 - 100 fc |4
| Detailed Work Areas | 75 - 100+ fc |5
Pro Tip: For general warehouse lighting, a target of 30 fc is a great starting point.
Step 2: Calculate the Total Lumens Needed
Now that you know the required foot-candles, you can calculate the total number of lumens needed to properly light your space.
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Formula: Total Lumens Needed = (Area in Square Feet) x (Target Foot-Candle Level)
Example:
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You have a warehouse that is 100 feet long by 50 feet wide.
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Area = 100 ft x 50 ft = 5,000 sq ft.
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Your target is 30 fc for general warehousing.
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Total Lumens Needed = 5,000 sq ft x 30 fc = 150,000 lumens.
This is the total amount of light your entire lighting system needs to produce.
Step 3: Account for Light Loss and Degradation
Light isn't a perfect system. Over time, factors like dirt, dust, and the natural depreciation of the LED will reduce the actual light output that reaches the floor. To ensure your lighting remains effective throughout its lifespan, you need to factor in a light loss factor (LLF).
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Scientific Principle: This accounts for lumen depreciation (L70, L80, etc.), fixture dirt depreciation, and room surface dirt depreciation. A typical LLF for a clean environment is around 0.85, while a dusty environment might be closer to 0.70.
Formula with LLF:
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Initial Lumens Required = (Total Lumens Needed) / (Light Loss Factor)
Example:
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Your warehouse is a relatively clean environment, so you use an LLF of 0.85.
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Initial Lumens Required = 150,000 lumens / 0.85 = 176,470 initial lumens.
This is the total lumen output your fixtures need to provide when they are new to ensure they hit your target foot-candle level over time.
Step 4: Determine the Number of Fixtures
Finally, you can calculate the number of UFO high bay lights you need by dividing the total lumens required by the lumens of your chosen fixture.
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Formula: Number of Fixtures = (Initial Lumens Required) / (Lumens per Fixture)6
Example:
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You've chosen a UFO high bay light with a lumen output of 24,000 lumens.
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Number of Fixtures = 176,470 initial lumens / 24,000 lumens/fixture = 7.35 fixtures.
Since you can't install a fraction of a fixture, you would round this number up to 8 fixtures.
Step 5: Create a Lighting Layout Plan
Now that you know you need 8 fixtures, the final step is to create a lighting layout plan to ensure they are evenly spaced for uniform illumination.
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Layout Rule of Thumb: The spacing between fixtures should be approximately equal to the fixture's mounting height.7 For example, if you're mounting your lights at 20 feet, the optimal spacing between fixtures is also about 20 feet.8
Example Plan:
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Warehouse Dimensions: 100 ft x 50 ft
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Number of Fixtures: 8
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Layout: You would install two rows of four fixtures each, spaced to cover the entire floor evenly.
(1) | (2) | (3) | (4) | ||||
(5) | (6) | (7) | (8) | ||||
By following this method, you can confidently determine the exact number of UFO high bay lights needed for your space, ensuring your investment results in a perfectly lit, safe, and productive environment. This systematic approach saves you money by preventing over-lighting and ensures you meet industry standards for optimal illumination.9