Most people still shop for light by wattage, which made sense when every bulb was a filament burning at roughly the same efficiency. With LED it tells you almost nothing. A 5 W LED and a 50 W halogen can produce identical light. The number that matters is the lumen — the actual quantity of light leaving the fixture.
The quick method
Multiply your floor area in square metres by the lux level the room needs. The result is roughly the total lumens you want in that room.
- Living room: 100–150 lux → a 20 m² room needs about 2,000–3,000 lm
- Bedroom: 100–150 lux → a 14 m² room needs about 1,400–2,100 lm
- Kitchen: 300 lux general, 500 lux over worktops → a 12 m² kitchen needs about 3,600 lm plus task lighting
- Bathroom: 200–300 lux, more at the mirror → a 6 m² bathroom needs about 1,200–1,800 lm
- Home office: 300–500 lux → a 10 m² office needs about 3,000–5,000 lm
- Garage or workshop: 300–750 lux depending on the work
- Warehouse aisles: 150–200 lux; packing and inspection areas 500 lux
Three things that change the answer
Ceiling height. Light spreads as it falls. A 3.5 m ceiling needs noticeably more lumens than a 2.4 m one to land the same brightness on the floor. Above about 4 m you should be looking at high bay fixtures with a narrow beam rather than ordinary ceiling lights.
Surface colours. A room with white walls and a pale floor can feel a third brighter than the same room in dark grey with oak floorboards. Dark interiors absorb light; add 20–30% to your total if yours is one.
Beam angle. A 1,000 lm spotlight with a 24° beam and a 1,000 lm ceiling light with a 120° beam contain the same light but behave completely differently. Narrow beams concentrate, wide beams fill.
Do not put it all in one fixture
The most common mistake is buying one very bright ceiling light and calling the room done. It produces flat, unflattering light and hard shadows. Spread the same lumen total across three or four sources at different heights — a ceiling light, a couple of wall lights or a floor lamp, and something task-focused where you actually work. The room will feel better lit at the same total output.
Where to find the number
Every product page in our store lists the lumen output in the technical specification table, along with lumens per watt so you can compare efficiency directly. If a retailer will not tell you the lumens, that is usually because the figure is not flattering.