Lighting lumen method calculator
Luminaire count and grid for a room by the lumen method.
Inputs
Worked example with the default inputs. The live calculator replaces it when the page loads.
- Room use
- Living room
- Room length
- 4 m
- Room width
- 3.5 m
- Ceiling height
- 2.4 m
- Luminaire height above the floor
- 0 m
- Working plane
- 0 m
- Target illuminance
- 0 lx
- Lumens per luminaire
- 800 lm
- Watts per luminaire
- 9 W
- Beam angle
- 90 °
- Reflectances, ceiling / walls / floor
- 70/50/20 %
- Maintenance factor
- 0.8
Luminaires
6
- Grid
- 3 by 2
- Spacing along
- 1.33m
- Spacing across
- 1.75m
- Illuminance the layout gives
- 156lx
- Lighting power density
- 3.86W/m²
This result is a design aid. Verify it against the current standard.
Calculation steps
- Floor area14m²
- Target illuminance150lxTypical design value. Not a standard’s value.
- Working plane0.7mAS/NZS 1680.1:2006 Table 3.2
- Luminaire height2.4mThe ceiling
- Height above the working plane1.7m
- Room index K = L × W / (Hm × (L + W))1.1
- Utilisation factor0.57Typical value for a direct luminaire. Use the maker’s table when you have it. Reflectances 70/50/20 %.
- Maintenance factor0.8
- N = E × A / (Φ × UF × MF)5.76
- Grid3 by 2
- E' = N' × Φ × UF × MF / A156lx
- Spacing to height, greatest1.03Spacing to height ratio for even light. Typical.
- Lighting power density3.86W/m²
Questions
Each answer describes what this tool calculates. The result is a design aid. Verify against the current standard.
What does the lighting lumen method tool do?
It finds how many luminaires a room needs for a target illuminance. The count is the target times the floor area. It divides that by the lumens of one luminaire and the two factors. The tool lays the count out as a grid and checks the spacing against the mounting height.
Where does the target lux come from?
A workplace room, such as an office or a warehouse, reads AS/NZS 1680.1:2006 Table 3.1, and the step names it. A house’s rooms, its kitchen and garage too, are in the AS/NZS 1680.2 series, which AmpSize does not hold. They and outside areas use typical values, and the tool says so. Table 3.1’s 240 lx is for workplace food preparation.
What is the utilisation factor?
It is the part of the lamp light that reaches the working plane. The tool reads a typical value for a direct luminaire. It uses the room index and the ceiling, wall and floor reflectances. Use the maker’s table when you have it: choose Own utilisation factor and type the value.