Industrial Lighting Lux Calculator

Heavy-duty lighting design suite for Warehouses, Factories, and Offices. Calculates fixture quantities using the Lumen Method (Zonal Cavity). Features a precise Maintenance Factor (MF) Builder for harsh industrial environments, detailed RCR analysis, and Power Density compliance checks.

Top-Down Layout View (Approximation)

E.g. 2x2 LED Panel (4000lm), High Bay (15000lm)

1. Room Geometry

Height from Workplane to Fixture

2. Maintenance Factors
3. Fixture Specs

Photometric Engineering Guide: Zonal Cavity Method

1. What This Tool Does

This software is a commercial-grade Photometric Calculator based on the IESNA Zonal Cavity Method (Lumen Method). It helps Electrical Engineers, Lighting Designers, and Facility Managers determine the optimal number of light fixtures needed to achieve a specific lux level in industrial and commercial spaces.

Unlike basic calculators, this tool accounts for complex variables like Room Cavity Ratio (RCR), Dirt Depreciation, and Surface Reflectance, ensuring that the designed system maintains adequate light levels even after years of operation (End-of-Life conditions).

2. The Physics of Photometry (Inverse Square Law vs. Lumen Method)

Light intensity follows the Inverse Square Law ($E = I / d^2$) for a single point source. However, in industrial spaces with multiple fixtures and reflective surfaces, calculating point-by-point is tedious. The Lumen Method solves this by treating the room as a "cavity" that integrates direct light and reflected light into a Coefficient of Utilization (CU).

$$ N = \frac{E \times A}{\phi \times CU \times MF} $$

Where:

  • N: Number of luminaires required.
  • E: Target Illuminance (Lux).
  • A: Area of the working plane ($m^2$).
  • $\phi$: Luminous flux per fixture (Lumens).
  • CU: Coefficient of Utilization (Efficiency of the room geometry).
  • MF: Maintenance Factor (Depreciation over time).

3. Room Cavity Ratio (RCR) & Efficiency

The RCR is a dimensionless number describing the room's geometry. It critically impacts the Coefficient of Utilization (CU).

$$ RCR = \frac{5 \times h_{rc} \times (L + W)}{L \times W} $$

Where $h_{rc}$ is the vertical distance between the fixture and the workplane (not the floor).

  • Low RCR (0-2): Wide, flat rooms (Offices). Light hits the floor directly. High Efficiency.
  • High RCR (>7): Deep, narrow rooms or High Bays (Warehouses). Much light is lost absorbing into walls before hitting the workplane. Low Efficiency.

4. The "Maintenance Factor" Trap

Amateur designs often assume MF = 1.0 or 0.9. In reality, industrial lighting degrades significantly. This calculator builds a realistic MF based on:

Factors of Decay

  • LLD (Lamp Lumen Depreciation): LEDs lose brightness over time. L70 means 70% brightness after 50k hours.
  • LDD (Luminaire Dirt Depreciation): In a factory, oil mist and dust coat the lens, blocking light.
  • RSV (Room Surface Dirt): Walls get dirty, reflecting less light.

A realistic industrial MF is often 0.65 - 0.75. Using 0.9 results in a system that is under-lit after just 2 years.

5. Frequently Asked Questions (FAQ)

What is the difference between Lux and Lumens?
Lumens (lm) measure the total quantity of visible light emitted by a source. Lux (lx) measures the intensity of that light as it hits a surface (Illuminance). 1 Lux = 1 Lumen per square meter. In lighting design, we start with the target Lux required for the task and calculate the Lumens needed to achieve it.
What is the Zonal Cavity Method?
Also known as the Lumen Method, it is the IESNA standard for calculating average illuminance in a room. It divides the room into three cavities (Ceiling, Room, Floor) and uses the Room Cavity Ratio (RCR) to determine how effectively fixtures can deliver light to the workplane based on reflection and geometry.
Why is Maintenance Factor (Light Loss Factor) important?
Lighting systems degrade over time. LED chips dim (LLD), and dirt accumulates on lenses (LDD) and walls (RSDD). If you design with a Maintenance Factor of 1.0, your system will be under-lit within months. Industrial designs typically use MFs between 0.65 and 0.75 to ensure target Lux is maintained at "End of Life".
What is a Room Cavity Ratio (RCR)?
RCR is a dimensionless number between 0 and 10 that quantifies the room's geometry. A low RCR (0-2) indicates a wide, flat room where light reaches the floor easily. A high RCR (7+) indicates a narrow, tall room (like a warehouse aisle) where light is lost absorbing into walls. It determines the Coefficient of Utilization (CU).
How many Lux do I need for a Warehouse?
Standards vary, but general guidelines are: 100-150 Lux for inactive storage/aisles, 200-300 Lux for active sorting/packing areas, and 500+ Lux for reading labels or fine picking. High-speed automation areas may require higher levels for sensor accuracy.
What is Lighting Power Density (LPD)?
LPD is the electrical power used by lighting per unit of area (Watts/m² or Watts/ft²). Energy codes like ASHRAE 90.1 set strict limits on LPD. Efficient industrial LED designs typically aim for an LPD below 5-8 W/m² depending on the ceiling height.
Does wall color affect lighting calculation?
Yes, significantly. Light bounces off walls and ceilings to reach the workplane. Dark walls (low reflectance) absorb light, reducing the Coefficient of Utilization (CU). White walls (high reflectance) improve efficiency. This calculator allows you to select reflectance profiles (e.g., 70/50/20).
What is the Stroboscopic Effect in industrial lighting?
This is a dangerous phenomenon where rotating machinery appears stationary due to the flicker frequency of the lighting. In factories with lathes or drills, this poses a severe safety risk. Industrial lighting must use high-quality drivers with high frequency (>1kHz) or DC output to eliminate flicker.