Inputs
Example Data
| Space | L | W | E | F | CU | LLF | HM | SC | W | |
|---|---|---|---|---|---|---|---|---|---|---|
| Bedroom | 4 | 3 | 150 | 1600 | 0.60 | 0.80 | 2.2 | 1.2 | 10 | |
| Kitchen | 5 | 4 | 300 | 2000 | 0.65 | 0.80 | 2.4 | 1.2 | 12 | |
| Open Office | 10 | 8 | 500 | 3200 | 0.65 | 0.80 | 2.6 | 1.3 | 28 | |
| Warehouse | 20 | 15 | 200 | 20000 | 0.55 | 0.75 | 8 | 1.4 | 150 |
Results
–
Recommended fixtures
Arrangement
– × –
columns × rows
Max allowed spacing
– m
by SC × HM
Actual spacing
– × – m
length × width
Estimated illuminance
– lux
from rounded fixture count
| Metric | Value |
|---|---|
| Area | – m² |
| Target illuminance | – lux |
| Lumens/fixture | – lm |
| CU × LLF | – × – |
| Max spacing | – m |
| Actual spacing | – × – m |
| Total wattage | – W |
| Energy cost (daily) | – |
| Energy cost (monthly) | – |
Formulas Used
- Fixture count:
N = ceil(E × A / (F × CU × LLF)) - Area:
A = length × width - Maximum spacing:
Smax = SC × HM - Arrangement: choose columns and rows so spacing ≤
Smaxandcolumns × rows ≥ N - Estimated illuminance from rounded N:
E' = N × F × CU × LLF / A - Total power:
Ptotal = N × Wfixture - Energy cost:
kWh = Ptotal × hours / 1000; cost =kWh × tariff
Use photometric values from manufacturer data. Verify against local codes and design standards.
How to Use
- Select units: SI for lux, Imperial for foot‑candles.
- Enter room length and width; override area if required.
- Set target illuminance and lumens per fixture from datasheet.
- Adjust CU, LLF, spacing criterion, and mounting height.
- Optionally add fixture wattage, hours, and tariff for costs.
- Click Calculate to get fixture count and layout.
- Export results as CSV or PDF for project documentation.
FAQs
Lumens measure light output from a source. Lux measures light arriving on a surface (illumination per area). The calculator sizes fixtures to reach your target lux or foot‑candles.
Use the fixture’s photometric report. CU depends on room proportions and reflectances. LLF aggregates lumen depreciation, dirt, and other maintenance factors.
SC indicates how far apart fixtures can be while maintaining uniformity, scaled by mounting height above the workplane. Maximum recommended spacing = SC × HM.
Yes. Switch to Imperial units; the form converts between foot‑candles and lux automatically for the calculation.
Results are engineering estimates based on standard point‑by‑point assumptions. Always confirm with detailed lighting layouts and local regulations.
Because fixture counts must be whole numbers, rounding up changes delivered illuminance. The tool shows the new estimate using the rounded number of fixtures.
Use the suggested columns × rows and spacing. Keep spacing ≤ SC × HM and align rows symmetrically for uniformity. Fine‑tune around obstructions and task zones.
Reference Data for Lighting Fixture Count
Recommended Illuminance by Space Type
| Space | Typical Target | Approx. fc |
|---|---|---|
| Bedroom | 100–150 lux | 9–14 fc |
| Corridor | 100–200 lux | 9–19 fc |
| Kitchen | 300–500 lux | 28–46 fc |
| Classroom | 300–500 lux | 28–46 fc |
| Open office | 300–500 lux | 28–46 fc |
| Retail | 500–1000 lux | 46–93 fc |
| Workshop | 750–1000 lux | 70–93 fc |
| Warehouse aisles | 150–200 lux | 14–19 fc |
Typical CU and LLF Reference Ranges
| Application | CU (typical) | LLF (typical) |
|---|---|---|
| Classroom | 0.65–0.75 | 0.80–0.90 |
| Open office | 0.60–0.70 | 0.75–0.85 |
| Corridor | 0.55–0.65 | 0.80–0.90 |
| Warehouse high‑bay | 0.50–0.60 | 0.70–0.80 |
Common Fixture Types and Typical Lumens
| Fixture type | Typical lumens | Notes |
|---|---|---|
| A19 LED (9–12 W) | 800–1100 lm | Residential rooms, lamps |
| 6″ downlight | 900–1200 lm | General ambient, residential |
| 4′ batten/strip | 1500–3000 lm | Utility, corridors, garages |
| 2×2 panel/troffer | 3000–4000 lm | Offices, classrooms |
| 2×4 panel/troffer | 3800–5000 lm | Offices, retail |
| Linear high‑bay (150 W) | 20000–24000 lm | Warehouses, factories |
Spacing Criterion Examples (Smax = SC × HM)
| Fixture | SC | HM | Smax (m) | Smax (ft) |
|---|---|---|---|---|
| Recessed downlight | 1.2 | 2.5 m | 3.0 | 9.84 |
| 2×4 panel | 1.3 | 2.6 m | 3.38 | 11.09 |
| Linear high‑bay | 1.4 | 8.0 m | 11.2 | 36.75 |
Values are typical planning references. Always confirm with manufacturer photometry and local standards.
Disclaimer: This tool is for preliminary sizing. Always validate with detailed photometric design.