Lampshade Size: The Two Ratios That Fit Any Lamp Base

A lamp that looks wrong is almost never a lamp problem. It is a lampshade size problem. The base is fine, the bulb is fine, and the shade sitting on top is two inches too small, so the whole thing looks like a person wearing a hat a size down.

The useful news is that shade proportions follow actual ratios, not taste. Three numbers and one eye level check will tell you whether a shade fits a base before you buy it, and they work on a thrift store find just as well as on a new lamp.

The Two Ratios That Do All the Work

Shade makers have settled on two proportions that keep a lamp looking balanced. Fenchel Shades states that the shade should be roughly two thirds the height of the lamp base, giving the example of a 15 inch base taking about a 10 inch shade, and that the width of the shade at its widest point should be about twice the width of the base, extending at least one inch past it on all sides. Their sizing guide covers the measuring method.

Those two ratios explain most bad lamps you have ever seen. A shade that is too short leaves the neck and socket exposed, and the lamp reads as unfinished. A shade that is too narrow makes the base look heavy and squat. Both are off by a couple of inches, which is exactly the margin people eyeball wrong in a shop.

Run the numbers on a common case. A 24 inch table lamp base wants a shade around 16 inches tall. If the base is 8 inches across at its widest, the shade wants to be around 16 inches across the bottom. Notice that those two numbers came out the same, which is why so many table lamp shades are roughly as wide as they are tall. That is not a coincidence, it is the two ratios agreeing.

Measure the Base Before You Measure Anything Else

Both ratios depend on the base measurement, and this is where people go wrong. The base height is floor of the lamp to the bottom of the socket, not to the top of the harp and not including the finial. The base width is the widest horizontal point of the body, which on a gourd or ginger jar shape is somewhere in the middle rather than at the foot.

Then take these three numbers for the shade itself, because shades are listed with all three and ignoring one is how you end up with a return:

• Top diameter. Across the narrow opening at the top.
• Bottom diameter. Across the wide opening at the bottom. This is the number the width ratio refers to.
• Slant height. Measured down the sloped side, not straight down the middle. On a tapered shade the slant is always longer than the vertical height, and listings usually give slant.

That last distinction catches almost everyone. If you want a shade that stands 10 inches tall vertically and you buy one listed at 10 inches of slant, the shade you get is shorter than you planned.

The Eye Level Test That Beats Every Ratio

Here is the check that matters more than any measurement, and it takes five seconds. Sit down where you will actually sit, at the height you will actually sit, and look at the lamp.

You should not be able to see the bulb, the socket or the switch. Fenchel notes the shade needs to be long enough to cover the neck, meaning the socket and the switch, when viewed at eye level. If any of that hardware shows, the shade is too short or sitting too high on the harp.

This test is why a lamp that works on a side table can fail on a desk. The seated eye level is different, so the same lamp that hides its bulb beside a sofa will glare at you across a desk. Position decides the answer, and that is also why bedside lamps have their own logic, covered in our guide to bedside lamp height.

One more safety number. Fenchel recommends keeping at least 2 to 3 inches between the bulb and the shade fabric, which matters most with older incandescent and halogen bulbs. If you are putting an LED in, heat is less of an issue, but the clearance still stops the bulb showing as a hot spot through the fabric.

Match the Shade Shape to the Base Shape

Proportion gets you most of the way. Shape is what makes a lamp look chosen rather than assembled.

• Drum shade, straight sides, same width top and bottom. Works on a straight or cylindrical base. The most forgiving shape and the safest default.
• Empire shade, narrow top and wide bottom with a strong taper. Pairs with a curved or urn shaped base, and throws more light downward, which makes it good for reading.
• Coolie shade, very wide bottom, very shallow slant. Casts a wide pool of light downward and almost none up. Suits a low, wide base.
• Rectangular or square shade. Use only on a square or rectangular base. A square shade on a round base reads as a mistake from across the room.

The general rule worth remembering is that the shade should echo the base. A round base takes a round shade. An angular base takes an angular shade. A heavily curved base is the one case where a plain drum works better than a matching curve, because two sets of curves compete.

How the Fitting Attaches, and Why It Matters

A shade that is the perfect size will not go on a lamp with the wrong fitting. There are three, and they are not interchangeable without an adapter.

• Spider fitting. The most common. Sits on a metal harp that rises either side of the bulb, held down by a finial. The harp height changes how high the shade sits, so a shade that looks slightly too low can sometimes be fixed with a taller harp rather than a new shade.
• Uno fitting. Screws directly onto the socket, no harp. Common on swing arm lamps and some floor lamps. The shade carries its own weight on the socket.
• Clip on fitting. Clips straight onto the bulb. Used on small accent lamps and chandeliers. Only works with the bulb shape it was made for.

Before you shop, look under your existing shade and identify which one you have. A harp swap is a few dollars and solves more problems than people realise, because raising or lowering a shade by an inch changes whether the socket shows.

Floor Lamps and Pairs Follow Slightly Different Rules

The two thirds height ratio is written for table lamps. On a floor lamp it produces something enormous, because a 58 inch base would call for a 38 inch shade. Nobody wants that.

For floor lamps, work from the top instead. The shade usually wants to be somewhere around 16 to 20 inches across the bottom and roughly 10 to 14 inches tall, sized so the bottom edge sits a little above the eye level of a seated person. The shade is doing a lighting job there more than a proportion job.

If you are buying a matched pair for two nightstands or two end tables, measure both tables first. Lamps only look like a pair when the shade bottoms land at the same height, and two tables in the same room are often not the same height. Our guide to nightstand height covers how to get that pairing right before the lamps arrive.

Fabric and Lining Change the Light, Not the Fit

Once the size is right, the material decides what the lamp is good for.

• White or off white linen and cotton. Light passes through, so the lamp lights the room. The default for general use.
• Dark or opaque shades. Light goes up and down only, not sideways. Dramatic, good for a moody corner, bad as a room light.
• Gold or warm lining inside. Throws a warmer coloured light down. Noticeably flattering in a living room, slightly yellow for task work.
• White lining. Neutral and brighter. The right choice next to a reading chair or over a desk.

A plain cream drum in good linen will out perform a fussier shade in nearly every room, which is worth knowing if you are replacing several at once. For how the lamp sits alongside everything else in the room, our guide to TV mounting height covers the sightline a lamp has to avoid blocking.

Frequently Asked Questions

What size lampshade do I need for my lamp base?

Start with two ratios. The shade height should be roughly two thirds the height of the base, and the shade width at its widest should be about twice the width of the base, extending at least an inch past it on every side. Then check at seated eye level that no socket or bulb shows.

Should a lampshade be wider than the lamp base?

Yes, always. The shade needs to extend at least one inch beyond the widest part of the base on all sides, and about twice the base width is the target. A shade narrower than the base makes the lamp look bottom heavy and leaves the bulb visible from the side.

How do you measure a lampshade correctly?

Three numbers: the top diameter, the bottom diameter, and the slant height measured down the sloped side rather than straight down. Shade listings usually quote slant height, so a tapered shade is shorter vertically than its listed number suggests.

Can I put any shade on any lamp?

Only if the fitting matches. Spider fittings sit on a harp and are held by a finial, uno fittings screw onto the socket, and clip on fittings attach to the bulb. Check which one your lamp uses before buying, and remember that swapping to a taller or shorter harp can adjust the shade height by an inch or two.

What shade size works on a floor lamp?

Ignore the two thirds rule, which would give you something far too large. Most floor lamps take a shade roughly 16 to 20 inches across the bottom and 10 to 14 inches tall, positioned so the bottom edge sits just above the eye level of someone seated nearby.

The Short Version

Shade height about two thirds of the base height, shade width about twice the base width and never narrower. Match round to round and square to square. Then sit down and look at it, because if you can see the socket, nothing else you got right will save the lamp.