Lamp shade, harp and fitter sizes

Fitter type first, harp height second, shade dimensions third - in that order. A shade with the wrong fitter will never fit no matter how good the dimensions are, and a harp an inch out is the reason a correctly-sized shade sits too high or shows the bulb. Most people check the dimensions and nothing else, which is why so many shades go back.

The good news is that two of the three are cheap to change. A harp is a few dollars, an adapter is a few dollars, and between them they rescue most mismatches without returning the shade.

Spider is the default and the one to assume unless the lamp tells you otherwise. Uno turns up on anything where the shade needs to point downward or sideways - swing-arm reading lamps especially - because there is no harp in the way. And note that threaded uno and slip uno are different: adapters are sold for each and they are not the same part.

A harp is sized by its height from saddle to finial screw. The saddle - the bracket it clips into at the socket base - is a separate dimension, and 3/8 inch is the standard almost everything uses.

Shades are quoted as three numbers in a fixed order: top diameter x bottom diameter x slant height. The third number is the measurement down the sloping side, not the vertical drop, and that is the one people get wrong. On a steeply sloped empire shade the slant can be two inches more than the vertical height.

For proportion against the base, three conventions hold up in practice:

• Width: the bottom of the shade about twice the width of the base at its widest point.
• Height: the shade roughly three quarters the height of the base, measured to the socket.
• Coverage: the shade wide enough that the socket and harp are hidden from a seated eyeline, which is the view that matters.

What the shade is made of matters at least as much as its size, and that is a separate question - a dark or heavily lined shade can halve what reaches the room. The numbers for that are in lamp shades and diffusion.

The default harp: the 9 in. set with a 3/8 in. saddle and finial. 9 inches is the commonest table lamp height, 3/8 in. is the standard saddle, and a finial is in the box - so this is the one part that fixes most shade-sitting problems outright. Two sets per pack covers a matched pair of lamps.
Who should skip it: anyone with an uno or clip-on lamp, which has no harp at all, and anyone whose lamp hardware is nickel or black - this is polished brass.

When the shade sits too low: the Saangseon 10 in. nickel harp. The one-inch-taller fix for a shade that lets the bulb peek out below, in nickel for chrome and brushed-steel lamps. Two per pack.
Who should skip it: anyone hanging a heavy glass or metal shade - this is published as light duty - and anyone who needs a finial, which is not included here.

When the fitter is wrong: the threaded uno bridge adapter. Bridges a spider shade onto a threaded uno lamp, which is the mismatch people discover after the shade arrives. Costs a fraction of a replacement shade.
Who should skip it: anyone with a slip uno rather than a threaded one - different part - and anyone with a clip-on shade, which this does not address.

The part that is always missing: the Creative Hobbies ELY505 brass finial. Solid brass, 1 in. tall, two per pack. A shade that will not sit straight on a second-hand lamp is nearly always a missing finial rather than a warped shade.
Who should skip it: anyone matching nickel or black hardware, and anyone whose harp uses a non-standard thread - check before ordering.

If the socket is dead or the cord is frayed, the shade is the least of it - rewiring a lamp covers the whole repair and what it costs.

If you are not sure what the parts are called, the parts of a light fixture is the full vocabulary for both lamps and ceiling fittings.

If the lamp itself is the problem, how to buy a lamp and the best table lamps start from scratch.