In this article, we are going to go over how to choose the right number of lights needed for any given space. Whether that be a gymnasium, warehouse, showroom or garage, CheapHighBays can help you! There are a few terms that we will use and I want to define them first.

  • A Lumen is the metric unit derived from the amount of visible light emitted by a light source. The higher the lumen count, the more light that source produces.
  • Lux (lx) is the metric unit that measures the intensity of light, as perceived by the human eye, when it hits or passes through a surface. One lux is equivalent to one lumen per square meter.
  • A Foot-candle is the non-SI unit that measures the intensity of light cast upon a surface widely used in the American lighting industry to calculate the adequate levels of light in one square foot. One foot-candle is equal to 1 lumen per square foot or about 10 lux.

Now that we know what a foot-candle, lux and lumen are, take a look at the table below showing the average foot-candle certain spaces need. To determine the foot-candles in a space, you must take into consideration the the task being performed. For example, putting together a 10 piece puzzle takes much less light than a 1000 piece puzzle.

Average foot-candles readings for different types of spaces and tasks


Space Type Examples Average Foot-candles
Public spaces with dark surroundings
Corridor, night light, waiting room, parking lot
2-5
Simple orientation for short temporary visits
Auditorium, dining room, waiting room
5-10
Working/living spaces where visual tasks are occasionally performed
Lunch/break room, exhibition halls, locker room, large component manufacturing
10-20
Performance of visual tasks of high contrast or large size
Conference room, open warehouse, auto sales lot
20-50
Performance of visual tasks of medium contrast or small size
Auto showroom, gymnasium, small component manufacturing
50-100
Performance of visual tasks of low contrast or very small size
High precision manufacturing, professional gymnasium
100-200
Performance of visual tasks of low contrast or very small size over prolonged period of time
Medical procedure room, jewelry and watch manufacturing
200-500
Performance of prolonged and exacting visual tasks

500-1000

Sources:


To demonstrate how this information is useful to you, let’s do an example.

I have a 30 ft by 60 ft manufacturing warehouse. Adequate light is needed to perform tasks in this space. I check out the foot-candle suggestion chart above and it looks like I need about 50 footcandles.

Warning. Math will be performed below! Don’t worry, it is very simple and no memorization is necessary!

Step 1: Multiply the room dimensions (in feet) together to determine the square footage of your space.

  • 30 ft x 60 ft = 1,800 SQ FT

Step 2: Refer to the chart above, general manufacturing needs about 50 foot-candles of light.

Since 1 foot-candle is roughly equivalent to 1 lumen per square foot, we must multiply the required foot-candle measurement by the square footage of the room to get the number of lumens in the light we need.

  • 50 (lm sq ft) x 1,800 (sq ft) = 90,000 lm

Step 3: Using the amount of lumens we need, we can determine which fixture we like and how many we need to purchase in order to get the light levels we need!

Take the total lumens needed (from step 2) and divide by the lumen count of your desired fixture. This will give you the quantity of lighting fixtures you need for your space!

  • 90,000 (lm) / 19,448 (Dome High Bay lumen count) = 5 Dome High Bay fixtures.

Lumen count for some of our best selling fixtures:

There are other factors to consider when illuminating a space. For example, mounting height, reflectivity of floors and walls and fixture spacing. This post is meant to help you get started and have a great starting point for switching to CheapHighBays LED high bays.