Inseam refers to the inner length of pants from crotch to foot.
The inseam is an important number to know when buying pants and jeans. The inseam is the lenght from the crotch and all the way down to where the pants end.
Tall guys normally use inseams of 36″, 38″ or 40″, which is not easy to find. Some Tall Shops offer pants in these longer lenths, and some even offer pants that are unfinished. These are to be sewn by oneself in order to get the length right.
Measure your inseam with a measuring band by laying a good pair of jeans down flat and measure the lenth of the leg along the inner seam.
Thanks to Land’s End for the nice illustration.