To find the diameter of a pendant or ceiling light, add the length and width of the room in metres, then multiply by 8: the result is the diameter in centimetres. A 4 × 5 m living room calls for a light of about 70 cm; a 1 × 4 m hallway, 40 cm. Above a table, it is the table that sets the rule, not the room.
The formula for a room
(length + width, in metres) × 8 = diameter in cm. It applies to a single light in the centre of a room and gives a starting point. Then adjust:
- + 10 to 20% if the ceiling is higher than 2.80 m, if the room has no tall furniture, or if the light is visually light (clear glass, openwork structure).
- − 10 to 20% if the ceiling is low (under 2.40 m), if the light is dense (stone, solid wood, opaque shade) or if it is not the only one.
| Room | Typical dimensions | Recommended diameter |
|---|---|---|
| Hallway, toilet | 1 × 3 to 1.5 × 4 m | 25 to 40 cm |
| Entrance | 2 × 2 to 2.5 × 3 m | 35 to 45 cm |
| Bedroom | 3 × 3.5 to 4 × 4 m | 50 to 65 cm |
| Kitchen | 3 × 3 to 3.5 × 4 m | 45 to 60 cm (or several small ones) |
| Living room | 4 × 5 to 5 × 6 m | 70 to 90 cm |
| Large open-plan living space | 6 × 8 m and above | 100 cm and above, or several lights by zone |
Above a table: the two-thirds rule
When the light is above a table, forget the room. The diameter should be half to two-thirds of the table’s width, and never extend beyond the table by more than 15 cm. For a 120 cm round table: 60 to 80 cm. For a rectangular table 90 cm wide: 45 to 60 cm, and two or three lights if it is long.
The hanging height has its own rule, 75 to 85 cm above the tabletop, detailed in How high should you hang a light above a table.
How does the shape change the perceived diameter?
Two 60 cm lights do not take up the same space in the eye:
- A flat disc looks smaller than a sphere of the same diameter, because it has almost no height. The Wabilo pendant, an 80 or 100 cm disc in micro-cement, works in a 20 m² living room where an 80 cm sphere would overwhelm.
- A sphere fills its whole volume. The Papira paper sphere, from 50 to 100 cm, is best taken large in a bedroom with a high ceiling and small everywhere else.
- An openwork shape (woven bamboo, wires, open structure) can be taken 20% larger: you see through it. The Denvia bamboo pendant comes in 45 to 75 cm for this reason.
- Clear glass behaves like an openwork shape. The Glazo globe, from 15 to 50 cm, multiplies rather than grows: three 30 cm globes in a cluster equal one 60 cm light.
And for a ceiling light?
A ceiling light is less visible than a pendant, because it stays flush with the ceiling. The formula still applies, but the effect is softer: you can go to the top of the range without weighing things down. In a bedroom of 3.5 × 4 m, a 60 cm ceiling light is comfortable. The Sylvoa ceiling light with its wooden ring comes in 30, 38 and 48 cm, which covers everything from the hallway to the bedroom.
In a hallway or a toilet, a small, very compact model is enough, and it is actually the material that matters more than the size: the Travoa travertine ceiling light is only 12 cm, and that is what gets noticed.
Several small ones or a single large one?
As soon as the room exceeds 25 m² or has several uses (dining area, sofa area, desk area), a single large centred light lights everything poorly. Prefer one light per zone, each sized for its zone: a 70 cm disc above the table, a floor lamp near the sofa, a lamp on the desk. Diameters are then calculated zone by zone, not for the whole room.
Common mistakes
- Choosing too small. This is the most common mistake: a 30 cm light in the centre of a living room looks like an afterthought. If in doubt, take the size up.
- Measuring the light without the ceiling rose or the cable. A 50 cm sphere under 40 cm of cable takes up 90 cm of height: check the clearance under the light.
- Forgetting wardrobe doors and windows. A wide pendant in the centre of a bedroom can get in the way of opening a wardrobe.
- Not checking the diameter on site. Cut a circle of newspaper to the chosen diameter, hang it with a piece of string, and look from the doorway. Two minutes that save a return.
Frequently asked questions
What diameter pendant for a 20 m² living room?
For 4 × 5 m, about 70 cm for a dense light, up to 80 or 90 cm for a flat disc or an openwork model.
What size pendant above a kitchen island?
Several small ones: 15 to 25 cm each, spaced 60 to 75 cm apart. Details in Lighting above a kitchen island.
Can a ceiling light be larger than a pendant in the same room?
Yes, by 10 to 15%, because it stays flush with the ceiling and does not cut into the volume of the room.
What diameter for a 12 m² bedroom?
For 3 × 4 m: about 55 cm. If the bed is under the light, go down to 45 or 50 cm so you do not have a mass above your head.
To remember: (L + W) × 8 for a room, half to two-thirds of the width for a table, and one light per zone as soon as the room is large. To compare sizes, browse our pendant lights and our ceiling lights, most of which come in several diameters.