Leotard sizing guidelines

All brands of leotards are very different!  I'll take you through several common brands I am familiar with and give you the low down on sizing.

I'll start with the difference between children's and adult sizing.  In most brands, the children's large is approximately a size 12/14 in regular kids' clothing.  Adult extra small or petite is usually about a size 0 in juniors or adults.  The length of these two sizes is usually similar with the adult extra small being slightly longer.  However, the adult extra small is usually much thinner in width than the children's size.  

As far as brands go, each is very different.  While I do have personal preferences, I'm trying to give a very objective review.  I will be discussing adult sizes only.

Bloch:  Bloch (including Jozette and Mirella) leotards run a tiny bit short.  Basics and cotton leotards seem to be short and thin, but they are very stretchy.  Fashion leotards that are made of nylon, spandex, etc. seem to run more short and wide.  The width makes up for the length when the leotards are worn, so all in all, they fit pretty true to size.  

Capezio:  Capezio leotards are very true to length, but they are thin in the width.  Barrel chested dancers or dancers with more apple shaped bodies may need a size larger to accommodate a wider torso.  The legs are kind of low cut, which is better for coverage, but not so great for lengthening legs.

Motionwear:  Motionwear leotards run extremely small in both length and width, and they do not stretch as much as other brands do.  This makes them really good for "holding in" the bust, tummy, etc.  All dancers should look at one size up.  Taller dancers or those with longer or wider torsos may need 2 sizes up.

Natalie:  Natalie Leotards run very true to size.  Like Capezio, they are a tad thin, but the size charts are pretty accurate.

Yumiko:  Yumiko leotards run pretty short and thin.  Dancers should order one size up.  That said, the leotards stretch, especially if they are not washed and dried often.  If you buy a Yumkiko second hand from E-bay, you could get away with the size recommended by the size chart.

Gaynor Minden:  Gaynor leotards run large, especially in the shoulders.  Dancers should look at the size recommended by the size chart or one size down.  The legs are also especially low cut, which is good for coverage, but not so good for elongating legs.

Eurotard:  Eurotard basic cotton leos run long, but true to width.  Dancers with long torsos should look at sizes recommended by the size chart.  Dancers with shorter torsos could look at a size smaller.  Eurotard nylon/spandex fashion leos run short and thin.  All dancers should look at at least one size up.

So Danca:  So Danca leotards run pretty true to size.  All dancers should look at the recommended size.

DanzMotion by Danzschuz:  DanzMotion leotards run extremely large.  All dancers should look at one size smaller than recommended.

Body Wrappers:  Body Wrappers leos run short and thin.  All dancers should look at one size up.

Grishko:  Grishko leotards run small in length and width, and especially shallow in the bottom area.  Curvier dancers will definitely want to look at a size up; dancers with less curves may be ok with the recommended size.

Sansha:  Sansha leotards run small.  They are also shallow in the bottom like Grishko.  All dancers should look at one size up.

Danskin: Danskin leotards run very large, especially in the shoulders.  All dancers should look at one size down, however dancers with very broad shoulders may be ok with the recommended size.

Mondor:  Mondor leotards run pretty true to size, but they are extremely high cut in the legs, so they don't cover the bottom area very well for curvier dancers.

These are all the brands of leotards I am familiar with at this point.  Hope this is helpful, and I'd love to hear some of your sizing guidelines in the comments!