Lighting Design Tool
Lux Calculator
Work out how many lumens and how many LED light fixtures your space needs. Enter the room size, application and fixture wattage — get required lumens, fixture count and a suggested grid layout instantly.
Lux / Fixture Count Calculator
Room & target
Target: 300–750 lux (retail general)
Result
Floor area
48 m²
Required light output
52,500 lm
Formula: total lumens = target lux × floor area × loss factor
Recommended fixtures
32 fixtures
Suggested layout
5 rows × 7 cols (35 positions)
How the lux calculator works
- Work out the floor area: length × width.
- Pick the target illuminance for your application (retail 300–750 lux, office 300–500 lux, warehouse 150–300 lux).
- Multiply: total lumens = target lux × floor area × loss factor (loss factors cover dirt, lamp depreciation and room utilization).
- Divide by the lumen output of your chosen fixture (fixture lumens = wattage × lm/W) and round up to get the number of fixtures.
Tip: use the beam angle calculator first to size the beam spread at your mounting height, then this lux calculator to size the quantity.
Recommended Lux Levels by Application
Common illuminance targets used by lighting designers (based on EN 12464-1 and CIBSE guidance):
| Application | Recommended lux | Notes |
|---|---|---|
| Retail store | 300–750 | Up to 1500 lux on displays and shelves |
| Office | 300–500 | 500 lux on work planes per EN 12464-1 |
| Showroom | 400–1000 | High vertical illuminance to flatter products |
| Hotel / Restaurant | 100–300 | Warm, layered ambient lighting |
| Museum / Gallery | 50–300 | 50 lux for light-sensitive exhibits |
| Warehouse | 150–300 | Uniform high-bay lighting |
| Industrial | 200–500 | Detail tasks may need 500 lux+ |
| Parking | 50–100 | Modest but uniform levels |
FAQs
Lux & Lighting Quantity Questions
Common questions about lux levels, lumens and how many fixtures you need.
How many lux do I need for a retail store?
General retail floors are typically lit to 300–750 lux, with 750–1500 lux on display focal points. For fashion and jewelry displays, higher vertical illuminance with good CRI (90+) is recommended.
How do you calculate lux from lumens?
Lux = lumens ÷ area in square metres. For example, a 1000 lm fixture over 10 m² gives 100 lux. In imperial units, foot-candles = lumens ÷ square feet.
How many LED track lights do I need for my space?
Divide the required total lumens (target lux × floor area × loss factor) by the lumen output of one fixture and round up. The calculator above does this automatically and suggests a grid layout.
What is the difference between lux and foot-candles?
Lux measures lumens per square metre; foot-candles measure lumens per square foot. 1 foot-candle = 10.76 lux. Our calculator supports both metric and imperial input.
Why do lighting calculations use a loss factor?
Real installations lose light to dust on fixtures, lamp depreciation over time and room surface absorption. A typical combined factor is 0.48–0.8, which is why we apply CU 0.6 × MF 0.8 (0.48) by default.
Need Help Specifying Your Lighting Layout?
Our engineers can prepare a photometric layout and recommend the right fixtures — free for qualified projects.