Indoor Lighting Illumination Lux & Lumen Method Calculator
Applies the standard zonal cavity lumen method per IS 3646 and NBC 2016. Computes room cavity ratio (RCR), dynamic coefficient of utilization (UF), luminaire count, maintained working plane Lux, and Lighting Power Density (LPD) with ECBC compliance benchmarking.
Governing Engineering Standards & Space Benchmark Allowances
Governing Standards & Formulas
- IS 3646 (Parts 1 & 2): Code of practice for interior illumination.
- NBC 2016 Part 8 Section 1: Building Services — Lighting and Natural Ventilation.
- ECBC 2017: Energy Conservation Building Code (Building Area & Space-by-Space LPD limits).
N_fixtures = ⌈(E_target × Area) / (Lumens × UF × MF)⌉
Actual_Lux = (N_fixtures × Lumens × UF × MF) / Area
LPD = (N_fixtures × W_fixture) / Area [W/m²]
ECBC 2017 & NBC Illuminance / LPD Reference Table
| Space Category | Recommended Lux | ECBC Max LPD |
|---|---|---|
| Commercial Office / IT | 300 – 500 Lux | 7.5 W/m² |
| Pharma / Cleanroom Assembly | 400 – 600 Lux | 9.5 W/m² |
| Industrial Workshop / Fabrication | 300 – 500 Lux | 8.0 W/m² |
| Storage / Warehouse Aisles | 150 – 200 Lux | 4.5 W/m² |
The Lumen (Zonal Cavity) method provides average horizontal illuminance on the working plane. It assumes uniform room geometry, standard surface reflectances (80% ceiling, 50% walls, 20% floor), and symmetrical fixture layout. It does not account for point-to-point uniformity ratios ($U_0 \ge 0.60$), unified glare rating (UGR ≤ 19), or task shading. High-precision architectural lighting layouts require point-by-point DIALux or AGi32 photometric simulation prior to fixture procurement.