How soon will a virgin female guppy gets pregnant?

If you put a male and a virgin female together, as long as the male guppy successfully impregnant the female guppy, she will get pregnant. The gestation period is usually 28 days or 4 weeks.

Virgin females can be bred as early as six weeks and as late as fourteen months, depending on the strain and environmental conditions.

Most breeders recommend that virgin females be bred in the range of three to six months. If you keep the male and females separate, the female will grow bigger and stronger than females raised with males.