Interior designers differ as to the appropriate length for curtains. The right hanging length for curtains depends on personal taste, the look of the room and the kind of fabric you use. Curtains should never be shorter than the window itself, yet curtain lengths vary, even within fractions of an inch.

Standard Options

Short-length curtains fall evenly along the base of the window or windowsill. They are suitable for active rooms like kitchens, where commotion and cleanup require open floor space. Window-length curtains can also make a room look wider. Lace curtains tend to look best hung short. Mid-length curtains fall between the windowsill and the floor. Interior designers tend to avoid this length. However, mid-length curtains in cotton or linen are a breezy compliment to cabins, cottages and sea-side homes.They offer some length without covering baseboards or wainscoting. Floor-length curtains are more formal and are often used in living, dining and bedrooms. They are always appropriate for tall or long windows and create a sense of height. When hanging sheer curtains layered with colored panels, floor-length curtains are a classic and tasteful choice.

Grazing, Dragging and Puddling

Floor-length curtains can be hung in different ways. Those that skim or touch the floor are referred to as grazing. A nice variation on grazing is to bring the hemline up 1/2 to 1 inch off the floor. This is a clean look that appears fitted and structured. Curtains that hang just longer than floor level are termed "dragging," whereas those that extend four or more inches longer than the floor are known as "puddles." Longer lengths should be arranged neatly at their base. Consider your fabric also. Sheer curtains look attractive at or above the floor, whereas the drama of velvet calls for dragging or puddling. Choose a length that suits your taste and design. Remember that curtains will shrink with washing. If you are unsure, err on the side of length. You can always take up the hem yourself or have it adjusted professionally.

Experimentation

Traditional curtain lengths can be limiting. They call for uniformity throughout a home or living space. They may be difficult to hang correctly. Longer curtains can be expensive and often need adjustment. Curtain lengths can get boring or clash with a changing design. Why not break the rules? The options for curtains should be as fresh and fun as fashion. Try an asymmetrical hem, which simplifies length and makes the curtain an object of interest. Or, mix curtain and panel lengths. As long as curtains hang evenly, you can play around with length.

Practical Considerations

Choose practically above all. If you have floor vents or gather dust beneath a window, floor-length curtains may not be for you. If you keep your windows open, shorter curtains are preferable.

Source:

EA Window - Curtain Panel FAQ