Lumens Not Watts: How Bright Should Each Room Be?
Watts tell you how much electricity a bulb consumes. They told you roughly how bright it was in the era when every bulb was a filament, and that era ended. An LED using 9 watts can produce more light than an old 60 watt bulb. The number to look for is lumens, and most people have no intuition for it at all.
The quick conversion, if you still think in watts
A traditional 40 watt bulb produced about 450 lumens. A 60 watt produced about 800. A 75 watt about 1100, and a 100 watt about 1600. If you know what a 60 watt bulb looked like in a room, you know what 800 lumens looks like.
The calculation for a whole room
Multiply the floor area in square metres by a figure between 100 and 200 lumens, depending on what happens in the room.
Use roughly 100 to 150 lumens per square metre for a living room or bedroom, 150 to 200 for a kitchen or bathroom, 200 or more for a workshop or a utility area, and 50 to 100 for a hallway.
A 20 square metre living room therefore wants around 2000 to 3000 lumens in total. A 10 square metre kitchen wants 1500 to 2000. A 4 square metre hallway wants 200 to 400, which is far less than most people install.
The important part: split the total
Two thousand five hundred lumens from a single ceiling fixture and the same 2500 lumens from five sources at different heights are two entirely different rooms. The first is flat and slightly clinical, the second has depth and shadow.
As a working rule, no single fixture should provide more than about half of a room's total. Three to five sources is the usual target for a living room: a ceiling or main fixture, one or two lamps at seating height, and one accent or wall light.
This is also what makes a room adjustable. With five sources you can run at 500 lumens for a film and 2500 for cleaning, without a single dimmer.
Task light is measured at the task
For reading, cooking or working, what matters is not the room total but the light landing on the surface. A 400 lumen lamp 40 cm from a book delivers far more usable light than a 1500 lumen ceiling fixture three metres away, because light falls off sharply with distance.
Useful targets at the surface: 300 to 450 lumens for reading, 500 to 800 on a kitchen worktop, 400 to 600 on a desk. A well placed adjustable lamp beats a brighter fixture in the wrong place every time.
Dark rooms need more, pale rooms need less
The calculation assumes fairly light walls. A room with dark paint, dark wood or a large amount of exposed brick absorbs a great deal of light, and you should add 20 to 50 percent to the total.
A pale Scandinavian room with white walls and a light floor does the opposite. Surfaces bounce light back and you can sit at the lower end of every range.
When in doubt, add sources rather than brightness
If a room feels dim, the instinct is a brighter bulb in the fixture you already have. That usually produces a brighter middle and the same dark corners.
Adding a second, modest source in the dark part of the room almost always works better, and it adds shape rather than just intensity. Our guide to layered lighting explains how the layers fit together.
Frequently asked questions
How many lumens does a living room need?
Roughly 100 to 150 lumens per square metre, so 2000 to 3000 lumens for a 20 square metre room. Split that across three to five fixtures rather than one.
How many lumens is a 60 watt bulb?
About 800 lumens. A 40 watt was around 450 and a 100 watt around 1600.
How many lumens do I need for reading?
Between 300 and 450 lumens delivered onto the page, which a small well aimed lamp achieves easily.
Is one bright ceiling light enough?
It can deliver the right total and still light the room badly. Several smaller sources at different heights produce depth and let you change the brightness by choosing which ones to switch on.
Do dark walls need more light?
Yes. Dark paint, dark wood and brick absorb a lot of light. Add 20 to 50 percent to the calculated total in a dark room.
Build the layers from floor lamps, table lamps and wall lights.