Unit Converter
Light Units: Lumens, Lux, and Illuminance
A practical guide to reading lighting specifications and checking illuminance values.
Workflow
Use this guide when a converted number affects lighting layouts, room brightness, photography notes, and equipment specifications. A reliable result keeps the original value, source unit, target unit, conversion factor, and rounding choice visible.
The goal is not to memorize every factor. The goal is to make the calculation traceable enough that someone else can review it later.
Checklist
- Use lux for light arriving on a surface, not total light output.
- Account for distance, spread, and fixture direction in real rooms.
- Use manufacturer photometric data for final lighting design.
Useful fact
Lumens describe output; lux describes received light per area.
Practical examples
1 lux equals 1 lumen per square meter.
A fixture can have high lumens but low lux if spread over a large area.
Illuminance decreases as light spreads over distance.
Frequently asked questions
What should I check first?
Confirm the source unit and target unit before changing the number.
When should I round?
Round at the end, after formulas and related conversions are complete.
Which calculator should I use next?
Use the related calculators below to check the main values from this guide.
Related calculators
Key takeaway
A useful conversion is traceable: it shows the original unit, the target unit, the factor used, and the rounding decision.