If my pant size is 14, and my bra size is 38DD...what is my dress size?

Dress sizes depend on both height and figure type. A junior size
corresponds to a height between 5'2" and 5'5" with a slender figure. A
misses size corresponds to a height between 5'5" and 5'7" with a well
proportioned figure. A women's size corresponds to a height between
5'5" and 5'8" and a fuller and rounder figure. The women's sizes DO
NOT correspond to bust measurements. A half size is somewhat shorter
than a misses size and a bit fuller and rounder. A petite size is
somewhat shorter than a misses size, with heights running from 4'8" to
5'4". The more expensive the dress, the more likely the manufacturer
is to label the dress with a size or two smaller than its true size.
Brassiere sizes consist of the band size (a number) and the cup size
(a letter). The band size is found by measuring around the rib cage
just below the bust line, adding 5, and rounding up to the nearest
even number. The cup size is found by measuring along the fullest part
of the bust and subtracting the band size. The letters correspond to
the result as follows: A (1"), B (2"), C (3"), D (4"), DD (5"), and
DDD (6").

-RR

Dear jitamix, 

Dress sizes are variable from manufacturer to manufacturer and style
to style.  The best thing to do is check your measurements in inches
(hip, bust, waist) against a size chart for the particular
manufacturer of the dress you are interested in.  Otherwise, the sizes
on a generic chart are only guides, so some variances will exist.

Also, American dress sizes do not compensate for large differences
between the top and the bottom of a person.  They are generally sized
to fit an all over small, or an all over large woman.  Therefore, you
are going to have consider the style of the dress.

According to the charts that I have found (they are listed below),
according to your pant size, you should wear a size 14 dress. 
However, according to your bust size, you should wear a size 22-24. 
You may not be able to find an off the rack dress that actually fits
you well all over.

Good luck with this.  
PbA

 I have listed several different size charts that are on the web. 
Wylde Enterprises 
http://www.wylde.com/Sizes.htm

African Style Measurements
http://www.africastyles.com/size-chart.html

Buffalo Arms Company
http://www.buffaloarms.com/page.htm?PG=clothsizechart