[header] How to identify male and female guppies [title] Check for a slender or round body shape. [step] The body shape of male and female guppies is very different and distinctive. Male guppies usually have very slender, long bodies, while female guppies are usually a lot rounder and bigger than the males, sometimes twice as big as a male guppy. 
[substeps] If your female guppy is pregnant, her body may look boxy or stuffed and even lumpy. She may grow even rounder as she gets closer to birthing her young.