Calculator Inputs
Provide your luminaire output and space data. CU and LLF vary by room reflectance, optics, dirt, and maintenance.
Formula Used
The calculator uses the lumen method to estimate average illuminance on a work plane:
If you enter a target illuminance, the required number of fixtures is estimated as: Nreq = ceil( Etarget x A / (Phi x CU x LLF) ).
How to Use This Calculator
- Enter lumens per fixture from the product data sheet.
- Enter the number of fixtures covering the selected area.
- Choose Length & Width or Area-only input mode.
- Set CU and LLF based on your project assumptions.
- Optionally add a target lux to check compliance.
- Click Calculate to display results above the form.
- Use the download buttons to export your report.
Example Data Table
Sample scenarios to illustrate typical inputs and expected lux ranges.
| Area Type | Area (m2) | Fixtures (N) | Phi per Fixture (lm) | CU | LLF | Estimated Eavg (lux) |
|---|---|---|---|---|---|---|
| Site Corridor | 60 | 10 | 2400 | 0.55 | 0.75 | 165 |
| Small Office | 48 | 8 | 3600 | 0.60 | 0.80 | 360 |
| Workshop Bay | 120 | 12 | 6000 | 0.62 | 0.78 | 363 |
| Warehouse Aisle | 180 | 14 | 9000 | 0.50 | 0.72 | 252 |
| Outdoor Yard | 500 | 12 | 20000 | 0.40 | 0.70 | 134 |
Illuminance Planning Notes for Construction Lighting
1) Why illuminance matters on site
Illuminance (lux) describes how much light reaches the working plane. Higher lux improves task accuracy and hazard recognition, while low lux increases rework and incident risk. Use this calculator early to balance visibility, energy, and fixture quantities before procurement.
2) Typical target lux ranges by task
Targets vary by project standards, but these ranges are commonly used during planning: walkways and corridors 100–200 lux, offices and general admin areas 300–500 lux, workshops and assembly bays 300–750 lux, warehouse aisles 150–300 lux, and outdoor yards 20–100 lux. Set your target lux input to reflect the most critical task in the space.
3) Selecting CU and LLF with realistic data
The utilization factor (CU) depends on fixture optics, mounting height, spacing, and surface reflectance. The light loss factor (LLF) accounts for lamp depreciation, dirt accumulation, and maintenance cycles. For temporary or dusty conditions, LLF may drop below 0.75. Document assumptions for audits.
4) Layout and spacing checks you can interpret
When you enter length, width, and a grid layout, the calculator reports approximate fixture spacing and spacing-to-mounting-height ratio (SHR). As a practical check, overly large SHR values can indicate non-uniform lighting, even if average lux appears sufficient.
5) Using results for procurement and verification
The “Effective Lumens” output shows how CU and LLF reduce delivered light. If your target is not met, the calculator estimates the required fixture count using the same assumptions. Use the CSV/PDF exports to compare options and validate changes during site modifications.
FAQs
1) What is the difference between lux and lumens?
Lumens measure total light output from fixtures. Lux measures how much of that light lands on a surface per square meter. This calculator converts fixture lumens into average lux for your area.
2) Which CU value should I use?
Use CU from luminaire photometric data or manufacturer tables for your mounting height, room proportions, and reflectances. If unknown, start with 0.50–0.65 and refine when the fixture is selected.
3) How do I choose LLF for construction environments?
LLF depends on dirt, aging, and cleaning frequency. Cleaner indoor areas may use 0.80–0.90. Dusty temporary work zones often use 0.65–0.80. Record the maintenance interval behind the chosen value.
4) Does this tool check uniformity?
It estimates average illuminance. Uniformity requires detailed photometric modeling. However, the optional spacing and SHR notes help flag layouts that may produce bright and dark patches.
5) What area should I enter for irregular spaces?
Use the illuminated footprint where the task is performed. For irregular shapes, break the space into rectangles, sum their areas, or use the Area-only mode with a measured total area.
6) Why does the required fixture count change so much?
CU and LLF significantly affect delivered light. Small changes in either factor can increase the needed fixtures. Verify photometric data, mounting height, and maintenance assumptions before purchasing.
7) Can I use this for outdoor floodlighting?
Yes, for a quick average estimate over a defined yard area. Outdoor performance also depends on aiming, glare, and spill control, so confirm final design with a lighting plan and on-site measurements.