This is not strictly speaking an antiques question, but in that many of us are dealing in décor, it is an important question to have answered. I have selected dining room chandelier because it is the most common need. You can apply the principals I will delineate to all ceiling fixtures in any location around a home.
The first proposal I would like to make is that the question is the wrong one or conversely/perversely, the buyers should ask themselves a different question first. What sort of décor do you want? Scale is not an absolute. The analogy I use relating to the flexibility of scale is jewelry. After all chandeliers are like necklaces or pendants and sconces are like earrings, in that they often come in pairs and flank something such as a mirror. On any given day, a woman might wear a small diamond solitaire around her neck or, when visiting Santa Fe, a large squash blossom necklace with big chucks of turquoise. You would not ask what size necklace is appropriate for this woman’s neck or chest, would you? With lighting as with jewelry, it comes down to the effect you are trying to create. What do you want to be elegant or flamboyant, serious or fun loving, extravagant or understated? A dining room chandelier can be a small elegant object or a grand baroque one. It is all about the effect. In addition, the bulk of a chandelier is often as important as the actual dimensions. By bulk I mean the impression of mass a light has, fat arms, dark round shades, or a deep bowl on the bottom as well as many other forms convey a feeling of bulk that can often compensate for dimension. If the light sits in a large open room with a high ceiling, a bulky light will be less likely to have that lost-at-sea appearance. Conversely, the spindly light with multiples of thin light colored arms can be of enormous dimensions and still not overpower a smaller room.
Sorry, I misled you in at the beginning of this post. You thought I was going to tell you exactly how big your dining room chandelier should be and now I seem to be backing out. You would really rather some simple geometry wouldn’t you; something such as the diameter of a dining room chandelier should be should be thirty seven and a half percent of the square inches of the tabletop. Believe me customers have come into my store having been told such nonsense. I usually tell them that this is the equivalent of telling Picasso that all his paintings should be three by five. Of course, common sense tells you that you do not want the dining room chandelier to be of a larger diameter that the table unless you have a fifteen-foot ceiling and the light hangs ten-feet off the floor. Ops, an exception. I will say that after thirty-five years selling dining room chandeliers I do find some conventions. The majority of my customers with average sized dining rooms and tables that seat six to eight ultimately choose a lights anywhere from eighteen to twenty four inches in diameter.
The only fixed math I can give you is how low you want the light to hang. I am going to invert this since ceiling heights vary so much. I speak in terms of how far off the floor the light should be since in most homes the floor is always in the same place. I will give you all the standards for ceiling fixture placement. Above a table, the light should be five to six feet from the floor. In any place where you walk under the light such as a hall, living room, bath, or bed room six foot ten inches to seven foot from the floor. Over a kitchen island six feet to six feet six inches from the floor. The point of these measurements is the assumptions that you want the light to be a visible element in the room. If you hang the light too high such that someone has to look way up to see it, the light will not have as strong an effect. In addition, a chandelier, table, and chairs are an ensemble, much like a couch, coffee table, and end tables.
To be effective, the elements of the ensemble want to be a comfortable distance apart. Hanging your dining room light eight feet above your table is the equivalent of having your end tables five feet from your couch.
A personal anecdote, when I was first in business I would tell people the dining room chandelier should be thirty to thirty-six inches from the table. This is how the interior design books state it. My customers would always ask what that comes out to and I would measure up thirty inches for the tabletop then add the three feet. When I put my hand at the height of the table every single one of my customers would immediately say that their table was higher. This is because a table is so much larger than a hand and therefore feels closer to you. Try it. All dining room tables are twenty-eight to thirty-two inches high most are thirty inches. Because I found myself constantly having to defend my claim that tables are thirty inches I stopped doing it that way. Now I always tell my customers that the lights should be five to five and a half feet from the floor. I have yet to have anyone argue with me about the location of the floor.
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