Bradley Bayou, the former creative director and head designer for Halston, shows some of his designs in New York. According to Bayou, calling sexiness an exact science is a stretch; it's all about symmetry.

NEW YORK — To call sexiness an exact science is a stretch, but there is certainly a formula, says fashion designer Bradley Bayou.

Measurements have nothing to do with it. It's about symmetry.

"What we are attracted to, what we find sexy, are things that are symmetrical. Research backs that up," explains Bayou, who has written a new book called "The Science of Sexy" (Gotham Books).

"Women try to force their figures into fads and trends, even if they're not flattering to them, because they think they're 'sexy.' ... But it's really all about balancing the body."

Short hourglass shapes might consider jackets that fit snugly at the waist, perhaps adorned with a peplum, and skirts with either semicircles or A-lines. Tall boyish shapes would be better served by open necklines, such as a V or a scoop, and a pleated skirt or straight-leg pants with angled pockets, Bayou suggests.

"Everywhere you look in nature, it's always balanced. A tree is balanced, even looking, even though it's not exactly the same on both sides. Yes, you'll have imperfections, but if you pull it all together, they'll be balanced."

That makes sense to Randy Thornhill, a biology professor at the University of New Mexico who has studied the link between symmetry and physical attraction.

"The bottom line is developmental health. The general finding for animals — not just humans — is that as the individual begins development, optimal development is bilateral symmetry. Most don't achieve it," he explains.

Symmetry, whether most of us realize it or not, may signal that an individual can be a strong, healthy mate capable of producing healthy offspring, Thornhill says. It indicates an ability to deal with any environmental problems encountered in the person's life.

Thornhill's original research focused on facial symmetry, but, he says, further research has found the same thing with breasts, buttocks and thighs.

"With women, bodily symmetry is conveyed in the face but also how she mobilizes — how she walks, a more attractive gait. When dancing, symmetrical people are more attractive when they dance. It comes out in the grace and movement," he says.

That means the structure of your genes are more important than the size of your jeans.

Bayou, formerly the creative director at Halston, is known as a source of red-carpet gowns for Oprah Winfrey, Queen Latifah, Salma Hayek and Eva Longoria — women of varying body types. "All these women are sexy and they're all different. The one thing in common, though, is that they're not emaciated. If that's what magazines say is sexy, they're wrong."

He adds: "Every body is unique, and there are different pieces that will work on them."

Bayou's book aims to help women find the styles that work for them. He offers suggestions based on 12 basic body types, accounting for shape, height and weight. He tells you what to wear and what not to wear: Overt plunging necklines and micro minis usually fall into that second category.

The one thing that does look good on just about everyone is a wrap dress. "Thank God for Diane von Furstenberg," says Bayou. (Von Furstenberg first introduced that silhouette to the fashion world in the early 1970s, got it on the cover of Time magazine in 1976, and has included it in every variation imaginable in her collections ever since.)

How to accessorize it? With confidence.

"I find that most women — 99 percent, I'd say — are insecure about their bodies, and I'm talking about drop-dead gorgeous women. What I find sexy is self confidence. I'm trying to give those women confidence about their body. You can't change your body overnight but you can change the way you dress."

Other things to wear with pride are kindness and a sense of humor.

"I think everybody agrees that sexy comes from within," Bayou adds. "A runway model might not be sexy, but a size 10 or 12 shapely woman can be so sexy. She'll get more attention in the end if she's confident and funny."

Women spend too much time stressing about the little stuff, he says, not realizing that men can usually find something sexy about almost anyone. "Women think you need it all, but you really only need one part and make the most of it. ... People aren't born perfect."

In an 18-year couture career, Bradley Bayou has maintained that a woman needs to dress for her own body, not according to fads. That said, he has developed 10 "commandments" that he says apply to every woman who wants to look her sexiest. They're included in his book "The Science of Sexy" (Gotham):• Choose the right undergarments• Choose the highest quality fabrics you can afford — they hold their shape better• Don't force your figure into every style• Use your skin to advantage — a peek of flesh can instantly draw the eye to the spot you're showing off• Don't buy big-ticket trendy items• Learn to make fabrics and cuts work for you; they can appear to add or subtract weight• Ignore the size on the tag and concentrate on fit• Worship accessories• Prints and accessories must be in scale with the body• Wear the V-neck shape that looks good on every woman.

Talk show host Oprah Winfrey arrives at the 2002 Primetime Emmy Awards in a dress designed by Bradley Bayou.