Finding the appropriate length your pendant light should hang from the ceiling involves following a basic formula, then adjusting for your personal needs. Because pendant lights hang down far below the ceiling's surface, you must take into account the heights of the people who will be around the pendant light most. Pendants are usually hung over fixtures or furniture, so you don't need to worry about people walking into them, but if two people are standing or sitting on either side of the light, the pendant should not impede their view of each other.
Cut a piece of string to about 3 1/2 feet long.
Cut a piece of foam--the soft upholstery foam is fine, as is polystyrene--to roughly the shape of your pendant. Tie one end of the string to the top of your foam pendant.
Climb a ladder that allows you to reach the area where your actual pendant will hang and have a helper measure 30 inches above the surface the pendant is intended to light, such as a table or countertop.
Tape the foam pendant to the ceiling with heavy-duty masking tape so the bottom of the foam is at the 30-inch measurement.
Perform tasks at the table or other surface the way you normally would, noting whether the foam gets in your way visually or seems too high or too low.
Adjust the string length up or down an inch at a time until you have a height you like, then note that as the length for your real pendant.
Most smaller surfaces can be lit at about 28 inches above the surface top, while larger surfaces may warrant a height of 32 to 34 inches. The farther away the light is, the large the pool of light it casts will be, but it also loses brightness with distance. The 28- to 34-inch range is the best for most standard pendants.