160 lighting figures — a 20 m² living room needs 3000 lumens
For every meeting of 20 room sizes and 8 uses: the lumens you need and what each kind of lamp burns to make them. Watts measure electricity, not brightness, so the calculation starts from lumens.
Watts are not brightness
Watts say how much electricity a lamp draws; lumens say how bright it is. When every bulb was incandescent, "60 W" implied a brightness — but today an LED makes the same 800 lumens on 8 W where a filament needs 62 W. The number to read on the box is the lumens.
The floor is what gets measured
One lux is one lumen landing on one square metre, so the light you need is simply lux times area — a 20 m² living room at 150 lux wants 3000 lumens. The same room can differ more than tenfold by task: a hallway is fine at 75 lux, while sewing or soldering wants 1000.
Several lamps beat one
The same lumens crammed into one fitting light the spot beneath and leave the corners dark. Splitting them across several 800-lumen lamps softens shadows, and one failure no longer means a dark room.
The lamp type decides the bill
Equal lumens mean equal brightness; what changes is the electricity. An LED makes 100 lumens per watt, a filament 13 — nearly eight times apart. The monthly figure below assumes five hours a day for thirty days.
These figures are a starting point
A high ceiling or dark walls make the same lumens feel dimmer. A shade that traps light asks for more, and sometimes a desk lamp on the task beats lighting the whole room.
What the room is for
- hallway75 lux
- bedroom100 lux
- living room150 lux
- bathroom200 lux
- kitchen300 lux
- study or desk500 lux
- workshop750 lux
- fine detail work1000 lux
Find it by size and use
Light you need
3㎡0.9 In pyeong
4㎡1.2 In pyeong
5㎡1.5 In pyeong
6㎡1.8 In pyeong
8㎡2.4 In pyeong
10㎡3 In pyeong
12㎡3.6 In pyeong
15㎡4.5 In pyeong
17㎡5.1 In pyeong
20㎡6 In pyeong
23㎡7 In pyeong
26㎡7.9 In pyeong
30㎡9.1 In pyeong
33㎡10 In pyeong
40㎡12.1 In pyeong
45㎡13.6 In pyeong
50㎡15.1 In pyeong
60㎡18.1 In pyeong
70㎡21.2 In pyeong
80㎡24.2 In pyeong
How to read this
- The light you need is lux times floor area; the use decides the lux.
- Watts are only that light divided by the lamp’s efficacy — not a measure of brightness.
- Bulb counts round up from one 800-lumen lamp.
- Ceiling height, wall colour and shades are not in this calculation.
Frequently asked questions
Q. How many lumens does a living room need?
About 3000 for 20 m². The living-room target is 150 lux, multiplied by the floor area — roughly 30 watts of LED.
Q. What is the difference between lumens and watts?
Lumens are brightness; watts are electricity. The same 800 lumens costs 8 W as LED and 62 W as a filament.
Q. How many lumens was an old 60 W bulb?
Around 800. When buying LEDs, reading "800 lumens" is more reliable than "60 W equivalent".
Q. Why does a study need more light?
Reading needs the desk lit, not the floor, so studies are set at 500 lux — more than six times a hallway’s 75.
Q. Can I put it all in one fitting?
The lumens add up the same, but only the spot beneath gets bright. Splitting them softens shadows and one failure will not darken the room.