Lampshade size: the right proportion with the lamp base

Divide the total height of your lamp by three: that gives you the right lampshade height. For the diameter, aim for at least one and a half times the widest point of the base. The goal: light diffuses without showing the bulb, and the silhouette stays balanced.

How do you calculate the size of a lampshade relative to the base?

Take the total height of the lamp, socket and base included, then divide it by three. A 60 cm lamp therefore calls for a lampshade of about 20 cm. The diameter is measured across the widest point of the base, and must exceed it by at least 50%.

The one-third rule for height

This proportion rests on one simple thing: a lampshade that takes up a third of the total height hides the socket, lets the base breathe and keeps the silhouette readable. Below that, the bulb shows as soon as you come close and the lamp looks long-legged.

An out-of-the-ordinary base is handled case by case rather than with a formula. That is where a wide choice makes the difference: the lampshade collection brings together 789 references as of 28 September 2026, from bedside size to the large cone of a floor lamp.

• One third of the total height, never less than a quarter
• The socket stays out of sight when you look at the lamp at eye level
• The neck covers the socket and the ring, without letting a sliver of light through

Measuring the diameter at the widest point

Place the tape on the base at its widest point: a stocky base, a bulge, splayed legs. Multiply by 1.5 and you get the minimum diameter of the bottom of the lampshade. Below that, the base sticks out and the whole thing loses its balance.

A round base takes a cone as well as a cylinder, provided you stay within this ratio. The details of shapes are set out in our article on choosing a lampshade for a round lamp base.

Which lampshade size should you choose according to the height of the base?

Count one third of the total height, then adjust according to use: on a bedside table, a short lampshade keeps the light low; on a floor lamp, a large wide cone lights the room without dazzling. The base dictates the height, the use dictates the width.

If your base has a very slim stem, a wide bottom or a particular socket, it is better to have your base checked before ordering, measurements in hand.

On a bedside lamp

A 45 cm high bedside table calls for a lampshade of about 15 cm, no wider than the nightstand. Beyond that, the light goes too high and lights the wall instead of the page. A model whose total height approaches 70 cm is handled differently, as explained in our article on the 70 cm table lamp.

On a living room lamp or a floor lamp

On a floor lamp on a stand, the lampshade often takes up a third of a height that exceeds 1.40 m. A wide cone diffuses better there than a narrow cylinder, which concentrates the light towards the floor and leaves the top of the stem in shadow.

The height of the stem matters as much as that of the lampshade: our guide on floor lamp height details the reference points to follow depending on the room.

How do you calculate the template of a conical lampshade?

Measure the bottom diameter, the top diameter and the height. A successful cone keeps a steady slope between these three dimensions, and a neck set to the diameter of the socket, not that of the base.

The ratio between bottom diameter and top diameter

A bottom twice as wide as the top gives the classic slope, gentle and stable. A narrower gap leans towards the cylinder, a wider gap towards the bell.

• Gentle slope: the bottom is about twice the top, the most versatile gap
• Tight slope: the cone comes closer to the cylinder and hardens the silhouette
• Wide slope: the bell tops a stocky base but reduces light towards the floor

The neck and the socket

The neck is the ring that runs down from the lampshade to the socket. On a sample of 31 references from our catalogue as of 28 September 2026, the E27 base is declared on 97% of them, which simplifies replacement on a base already in place.

An old base, a ring socket or a smaller base require an adapter ring. The correspondences are detailed in our article on bulb base size.

Which material for which proportion?

Fabric softens and forgives small differences in proportion, metal and glass reveal them. On a slim, graphic base, a light material works better; on a massive base, an opaque lampshade holds the silhouette.

Linen and fabric

On a sample of 31 references from our collection as of 28 September 2026, linen is declared on 52% of them and fabric on 23%. These materials filter the light without hardening it, which makes a slightly wide lampshade visually acceptable.

They do, however, require regular care: our guide to cleaning a fabric lampshade gives you the steps to follow.

Metal and glass

Metal appears on 26% of the same sample, glass on 13%. Opaque metal concentrates the light towards the bottom and the top: the proportion must therefore be right, as no diffusion will come to hide a diameter that is too short.

Glass does the opposite: it lets the source show and projects a wider light, which forgives a slightly narrow cone. Our selection of glass lighting shows the result obtained on round shapes and spheres.

For a truly unusual base, the advice and inspiration page lets you handle the case individually, measurements in hand.

When proportion breaks: three mistakes

A badly proportioned lampshade does not show in a catalogue photo, but it stands out at once in a living room. Three faults recur: a diameter that is too small and leaves the bulb visible, a height that is too generous and crushes the base, a badly placed weight that makes the lamp tip over.

A lampshade narrower than the base

• Visible bulb: the source shows as soon as you sit next to it
• Glare: the light hits the eye directly instead of diffusing
• Unbalanced silhouette: the base looks heavy, the lampshade perched on top

A lampshade that is too tall or too heavy

• Tipping: a large cone on a slim stem shifts the centre of gravity
• Crushed base: beyond a third of the total height, the stem disappears
• Neck too short: the socket sticks out and the fitting holds poorly

Very large formats are therefore chosen according to the base, never on their own. Our article on the large lampshade details the cases where excess works.

When the hesitation is about style more than dimensions, the Designix Google listing gathers buyer reviews, verifiable in one click, on the selection and the finish of the pieces.