Lighting Layout Calculator — Lux Levels by Room Type

This calculator uses the lumen method recommended by CIBSE (Chartered Institution of Building Services Engineers) to determine the number of light fittings required for a given room. It takes into account the room type, size, light fitting output, and standard correction factors.

The lumen method formula

Total lumens = (Lux × Area) ÷ (Utilisation Factor × Maintenance Factor)

Number of fittings = Total lumens ÷ Lumens per fitting

Factors used

• Utilisation Factor (UF): 0.6 — typical for domestic rooms with light-coloured walls
• Maintenance Factor (MF): 0.8 — accounts for dirt accumulation and lamp ageing

Typical lux levels (indicative)

General-lighting targets derived from CIBSE Guide A (dwellings) and the SLL Code for Lighting. CIBSE publishes ranges for dwellings rather than a single fixed table, so these are indicative starting points — add task lighting where the activity needs it.

• Kitchen: 300 lux
• Living room: 150 lux
• Bedroom: 100 lux
• Bathroom: 150 lux
• Home office: 500 lux
• Hallway: 100 lux
• Garage / workshop: 300 lux

The calculator also determines an even rectangular grid layout and the spacing for uniform light distribution across the room. Where the lumen-method minimum does not fill a neat rectangle, it rounds the fitting count up to the next even grid.