Technical meaning
- Illuminance is the density of luminous flux arriving on a surface.
- In room and workplace estimates, the assessed surface might be a desk, bench, floor path, shelf face or other task plane named in the note.
Calculation use
- Illuminance can be estimated from delivered lumens divided by the assessed area.
- Required lumens can be worked back from a target illuminance, area, utilisation factor and maintenance factor.
Not the same as
- Illuminance is not total light output. Lumens describe output before the area and delivery assumptions are applied.
- Illuminance is not the whole lighting quality note. Glare, vertical brightness, contrast, controls and measurements remain separate checks.
Australian context
- Australian lighting notes should state the assessed plane and whether the illuminance value is a target, estimate or measured reading.
Examples
| Example | Value | Planning note |
|---|
| Desk plane | 300-500 lx planning context | The reading belongs to the work surface, not the whole office volume. |
|---|
| Known output check | delivered lumens / area | Use the lumens-to-lux calculator when output and area are known. |
|---|
| Maintained estimate | target adjusted by UF and MF | Delivery factors change the lumen allowance required for the target. |
|---|
Calculation limits and records
- Illuminance arithmetic is formula-based. Workplace, public-space and emergency-lighting decisions still need the applicable Australian source pathway.