3㎡ · office desk
1200
lm · 400 lux
3 m² office desk — 1200 lumens
A room at 400 lux needs 1200 lumens. That is 12 watts of LED, or 2 bulbs of 800 lumens.
Watts are not brightness
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.
- LED100 lm/W12 W
- fluorescent60 lm/W20 W
- halogen20 lm/W60 W
- incandescent13 lm/W92.3 W
- Light reaching the floor
- 400 lux
- Light you need
- 1200 lm
- Room size
- 3 ㎡
- In pyeong
- 0.9
- In 800-lumen bulbs
- 2
- A month of electricity
- 1.8 kWh
- Extra watts if incandescent
- 80 W
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.
Nearby cells
Same room, other uses
Same use, other sizes
3㎡ · office desk
1200lm
4㎡ · office desk
1600lm
5㎡ · office desk
2000lm
6㎡ · office desk
2400lm
8㎡ · office desk
3200lm
10㎡ · office desk
4000lm
12㎡ · office desk
4800lm
15㎡ · office desk
6000lm
17㎡ · office desk
6800lm
20㎡ · office desk
8000lm
23㎡ · office desk
9200lm
26㎡ · office desk
10400lm
30㎡ · office desk
12000lm
33㎡ · office desk
13200lm
40㎡ · office desk
16000lm
45㎡ · office desk
18000lm
50㎡ · office desk
20000lm
60㎡ · office desk
24000lm
70㎡ · office desk
28000lm
80㎡ · office desk
32000lm
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 for a 3 m² office desk?
1200 lumens — 400 lux times the floor area.
Q. How many watts should the lamp be?
12 W as LED, 20 W as fluorescent. An incandescent would draw 92.3 W — 80 W more.
Q. How many bulbs do I need?
2 at 800 lumens each. Spread them out rather than stacking them in one fitting.
Q. What does it cost to run?
On LED at five hours a day, 1.8 kWh a month.