Hard to label

When is a size not a size? When it pertains to women’s clothing.

This is not a Zen koan, but a fact of life in today’s retail world. Women, you may have noticed while shopping that at some point, you went from your regular size to the next size down, without actually losing any weight. This is called vanity sizing, and it has gained popularity among women’s clothing manufacturers because women apparently prefer to buy clothing in small sizes, even if those sizes don’t actually reflect reality.

Personally, I have no problem with this. In fact, my new plan is to proceed from a size 6 (formerly 8) to a size 4 while eating a creme brulee. But all vanity is not equal.

Women’s clothing sizes vary depending on where you shop. A medium at one place could be a small at the store next door, while across the mall you’ll manage to fit the extra small. (Lest men feel any “vanity size thy name is woman” superiority, parse this -- a fellow who wears a size large shirt anywhere else fits only the XXL size at Abercrombie & Fitch, according to a male staffer there. Apparently, men like to think they’re bigger than they really are, go figure.)

Further, vanity sizing hasn’t happened across the board. While most of the larger retailers are all for it, your higher-end boutiques in Los Angeles have long gone the opposite route. Not only do they refuse to vanity size, their designers go with European sizing -- Italian, French, English -- and on top of that, their sizes tend to run small. Let’s call it humility sizing.

And many boutiques don’t even carry larger sizes at all, even though the average American woman is now a size 14, according to a recent survey by the Textile/Clothing Technology Corp., a textile and apparel research firm based in Cary, N.C., where it’s no sin to be amply proportioned.

Then there are sizes that capture the imagination. Size 0 has been around for years, but Abercrombie started sporting 00 in 1996. When asked what double zero means, exactly, a sales clerk replied that she had no idea. (Most staffers at the various stores wished to remain anonymous.) When further asked where does one go from there, the answer was “the kid’s department.”

Like Alice in Wonderland, shrinking and growing beyond her control, women’s clothing inhabits a world with no absolutes. Lourdes Lozano, sales manager for a women’s line called Brasil Sul, said that depending on where you shop, “you want an active-wear pant in a medium, you get either a tent or a thong.” Lozano, who has worked in practically every area of women’s clothing, added, “It’s so frustrating. I’m in the business 25 years and I don’t know what size I am.”

The math here is enough to make E=mc2 look like child’s play. Consider the following equations found while shopping at some chain and discount stores and local boutiques:

2 = 4

Abercrombie & Fitch not only features the 00, but a woman who is a size 2 at, say, the Gap, is a size 4 here. (Bebe runs similarly small.) Then again, that could be reversed to 4=2, if you preferred to use the Gap as your base measurement. So, does that mean the Gap runs big or A&F; runs small? This isn’t a proper scientific study with a control group; the mice refused to try on the sweater sets. Let’s move on to something easier.

X = X + 1 1/2

J. Crew used to have a reputation for super-vanity sizing. A medium anywhere else could be a cozy extra-small here. But after a revamping last fall, the sizes have shaped up a bit. Now a medium at another store might be as big as a small here.

Everything’s at 6s and 7s

Target isn’t satisfied just catering to the even numbered among us. For example, its Mossimo women’s line starts at size 1 and runs up the odd-numbered slope. Other lines they carry use the evens, so you can find every number from 1 to 14. The plus size section continues the run up to 24. But actually finding a 1, 2 or 3 will prove difficult. The most popular sizes at the store on La Cienega are 6 through 8 and 12 through 14, according to staffer Linda Clark. The small numbers just don’t get much play.

4 = 8

At the other end of the Wonderland spectrum, try a boutique. M. Fredric at the Grove carries lines of contemporary clothing that run from 0 to 10, but the sizes run so small that a 0 elsewhere will be a 4 at this store, and a 12 elsewhere better just keep it moving, there’s nothing to see here.

1, 2, 3, 4

Make sense? Chico’s, the nationwide women’s clothing chain that caters to baby boomers, has thrown out all known sizes and made up its own system. So a size 3 Chico skirt would be a size 14 or 16 elsewhere. The management makes no bones about changing the size to suit its clientele.

“It makes you feel better,” said Carole Dailey, manager of the Grove store. “If I’m a size 0, psychologically it feels good. It’s not about what size it is anyway, it’s about how it fits.” And in another act of sartorial rebellion, Chico’s doesn’t carry anything smaller than a 4, er, a 0.

38 = 4 = 2

At Barneys New York, the sizes aren’t made up, they’re imported. Its Piazza Sempione department features Italian sizing that runs in even numbers from 36 to 48. A 36 translates to 2, 48 to 14. But the sizes run small, so throw that out the window and do your best.

You can also find English sizes, which run 8, 10, 12 and 14. In American, that’s small, medium, large and extra-large. There’s also French sizing, mon Dieu. (The Ron Herman women’s department at Fred Segal also carries the European Tower of Babel sizes.)

As a staffer said, middle America may be larger, but designers run smaller.

Given the oblique math involved, if you’re buying clothes for someone else, gift cards might be the way to go -- one size fits all.