A-line vs sheath

An A-line dress and a sheath dress can share the same neckline, the same length and the same fabric, and still look like opposites. The difference is entirely below the waist: the sheath keeps following the body, the A-line steps away from it.

The difference in one sentence each

A sheath is fitted from the bust through the waist and hips, then drops straight or tapers slightly to a hem near the knee. It is shaped with darts or seams and usually has a slit or vent so you can walk.

An A-line is fitted through the bodice to the waist, then widens in a steady, nearly straight line to the hem, so the skirt clears the hips and thighs. The hem is clearly wider than the hips.

Side by side

Which one to choose

Choose the A-line if your hips are your widest point, if you want to move and sit without thinking about it, or if you are buying online and can only be sure of your bust and waist size. It is the more forgiving of the two, and the one most often suggested as a first dress shape.

Choose the sheath if you want a sharp, tailored line, if your bust and hips are similar sizes, or if the occasion calls for something more formal. Because it fits in three places, it rewards trying on, or having it altered: taking in a sheath at the waist or letting out the hips is standard tailoring work.

The same proportions can feel very different on two people. If you are undecided, see both on yourself before buying.

How to tell them apart in a product photo

Listings often call both shapes "fitted" or skip the silhouette entirely. Three quick checks help:

• Follow the side seam below the waist. If it curves in again toward the knee, it is a sheath. If it keeps moving outward in a straight line, it is an A-line.
• Compare hip and hem. On a sheath the hem is about as wide as the hips or narrower. On an A-line the hem is clearly wider than the hips, even on a flat lay.
• Look for a vent. A slit or vent at the back or side hem almost always means a narrow skirt, which means a sheath or pencil shape. A-line skirts rarely need one.

Fabric, lining and length

Fabric changes both shapes. A sheath in a stretch crepe or ponte moves with you and forgives small size differences; in a woven fabric with no stretch, the fit at the hips has to be right. An A-line in a crisp cotton, scuba or wool holds its triangle away from the body, while the same pattern in soft jersey or viscose drapes down and starts to look like a shift.

Lining matters more for a sheath, because a lining helps a close-fitting skirt slide over tights and keeps it from riding up when you walk. Length shifts the mood of both: at the knee they read as office or daytime; at midi length the sheath becomes more formal and the A-line more relaxed. Very short A-lines tip into the trapeze and mini territory of the 1960s (see the history of fashion silhouettes).

If it almost fits

Because a sheath is fitted in three places, it is the dress most often altered: taking in the waist, letting out or taking in the hips and shortening the hem are routine tailoring jobs, as long as the seams have allowance. An A-line usually needs less: if the bodice fits, the only common alteration is the hem, which on a flared skirt follows a curve and takes a little more work than a straight hem.

The neighbors: fit-and-flare, shift and pencil

Two shapes are often confused with A-line. A fit-and-flare also starts at the waist, but the skirt flares immediately and fully, often as a circle, with folds and a wavy hem; an A-line widens in a straight, calm line. A trapeze widens like an A too, but from the shoulders, with no waist.

On the sheath side, a shift drops straight from the shoulders with no waist shaping, so it skims where a sheath fits. A pencil dress is a name shops often use for a sheath with a narrower, tapered skirt; the silhouette is the same family. A column is the long, straighter cousin of the sheath.

You can overlay any other pair yourself with the silhouette comparison tool, or read every shape in the dress silhouette guide.