For decades we thought of watts as brightness. A 60-watt bulb was “stronger” than a 40-watt one, and that rule of thumb worked — as long as everyone used the same technology. Since LEDs arrived, it no longer does: two LEDs with the same wattage can differ twofold in luminous flux. Watts measure consumption, not light.
What you are looking for is the lumen: the total amount of light a light source gives out. This article gives the total luminous flux each type of room needs, shows you how to work it out for your own room, and explains why a single ceiling light is not enough.
How many lumens does a 20 m² living room need?
A 20 m² living room needs roughly 3000–4000 lumens of total luminous flux, at a colour temperature of 2700–3000 K. That does not come from a single light: general lighting, ambient lighting and accent lighting add up to it together. With a low ceiling the lower figure is right; above 2.7 metres, the upper one.
Lumen table by room size
The table gives guide values for an average room with light-coloured walls and a 2.5–2.7 metre ceiling. It is a starting point, not the final word — the next section shows when to depart from it.
| Room | Floor area | Total luminous flux | Colour temperature |
|---|---|---|---|
| Living room | 20 m² | 3000–4000 lm | 2700–3000 K |
| Kitchen (worktop) | 12 m² | 3500–4500 lm | 3000–4000 K |
| Bedroom | 14 m² | 1800–2500 lm | 2700 K |
| Bathroom | 6 m² | 1500–2000 lm | 3000–4000 K |
| Study | 10 m² | 2500–3500 lm | 4000 K |
| Children’s room | 12 m² | 2000–3000 lm | 3000 K |
| Hallway | 5 m² | 800–1200 lm | 2700–3000 K |
How do I work it out for my own room?
Multiply the floor area of the room by the general lighting level it needs: 150–200 lux for a living room, 300 lux for a kitchen or study — and a separate 500 lux on a desk or kitchen worktop. The result is the number of lumens you need. An 18 m² living room at 175 lux: 18 × 175 = 3150 lumens.
Lux and lumens are not the same thing, and this is where they tend to get mixed up. Lumens tell you how much light the lamp gives out. Lux tells you how much light reaches a given surface — that is, lumens divided by square metres. That is why the lumens you need depend on the size of the room: the same lamp is plenty in a small bathroom and too little in a large living room.
There is no mandatory lighting standard for homes: the lux values per room are design guidelines, not requirements. The 500 lux recommended for a desk or kitchen worktop comes from the European standard for workplace lighting, EN 12464-1 — that is what it asks for on the task area for writing, reading and screen work in an office.
Three things push the result upwards:
- Dark walls and furniture. A light wall reflects light; a dark one absorbs it. With deep-coloured wall finishes, allow 20–30% more.
- A high ceiling. Above 2.7 metres, the light travels further before it reaches the level where you use it. Above three metres, take the upper value in the table, and preferably spread it across several light sources.
- Age. The eyes of someone over sixty need roughly twice as much light for the same visual performance as those of a twenty-year-old. If an older person uses the room, this is no minor correction.
Why is a single ceiling light not enough?
Because luminous flux on its own is not quality. If all 3500 lumens come from a single ceiling light, the room will be evenly, flatly bright — exactly like an office. At home that is rarely pleasant, and in the evening it is downright uncomfortable.
Lighting that works at home has three layers, each switched separately:
- General lighting — the overall lighting of the room. Roughly half to two-thirds of the total luminous flux. Ceiling lights, chandeliers, recessed spotlights.
- Task lighting — where you do something: a reading chair, the kitchen worktop, a desk, a mirror. These lights are targeted, and give enough light for the task on their own.
- Ambient and accent lighting — wall washers, picture lights, table lamps. Little luminous flux, big effect: this is what gives the room space and depth.
In the evening, the second and third layers are enough in most homes. If you only have a single switch, it is either glaring or dark — there is nothing in between.
How many watts of LED is 3000 lumens?
Roughly 25–30 watts, but you cannot work backwards from that. LED efficacy varies between 80 and 210 lm/W from model to model — the same wattage can mean twice the luminous flux. Always look at the lumen value; use the watts only to estimate your electricity bill.
| Old bulb | Luminous flux | LED equivalent |
|---|---|---|
| 25 W | ~230 lm | 3–4 W |
| 40 W | ~430 lm | 5–6 W |
| 60 W | ~730 lm | 8–9 W |
| 75 W | ~950 lm | 10–12 W |
| 100 W | ~1350 lm | 14–16 W |
The equivalent wattage (“equivalent to 60 W”) cannot be stated freely: the table in Regulation (EU) 2019/2015 sets which luminous flux corresponds to which bulb wattage — 25 W: 249 lm, 40 W: 470 lm, 60 W: 806 lm, 75 W: 1055 lm, 100 W: 1521 lm; values in between are calculated proportionally. These are somewhat higher than the typical output of old bulbs, so an LED correctly labelled “equivalent to 60 W” gives no less light than an old 60-watt bulb.
Where the figures come from: luminous flux is stated on the manufacturer’s datasheet, but the real value may differ from it. That is why the table gives ranges rather than exact targets. The figure comes from the manufacturer’s photometric measurement; under the EU ecodesign regulation (2019/2020), it has to be shown on the box and on the datasheet.
Frequently asked questions
Are more lumens always better?
No. Too much light is just as uncomfortable as too little: it dazzles, and in the evening it makes it harder to fall asleep. The aim is not the maximum but the level that suits what the room is used for — in several layers that can be switched separately.
Does colour temperature matter as well as luminous flux?
Yes, and many people underestimate it. The same 3000 lumens is warm and homely at 2700 K, and cold and office-like at 6500 K. Luminous flux is the quantity, kelvin the character of the light — for living spaces, 2700–3000 K is almost always the right choice.
What should I do with my old light fitting?
Most old light fittings have an E27 or E14 lamp holder, so an LED light source simply screws in. Check the maximum wattage marked on the fitting: a limit set for incandescent bulbs will practically never hold an LED back, because an LED gives the same light from a fraction of the watts.
Sources
- Commission Delegated Regulation (EU) 2019/2015 on the energy labelling of light sources, EUR-Lex — the table in Annex V assigns an equivalent incandescent wattage to each luminous flux (60 W = 806 lm).
- licht.de: Leitfaden DIN EN 12464-1 (licht.forum 60) (in German) — the German lighting industry association’s guide to the standard for lighting indoor workplaces (EN 12464-1:2021), with an office example: 500 lux on the task area.
- Signify (Philips): MASTER LEDbulb 4-60W E27 827 A60 datasheet — 4 W, 840 lm, 210 lm/W, energy class A: the top end of today’s LED bulb efficacy.
