Couple questions to help figure this out, first, are these photoperiods or autoflowers? What's your general location? Are these only growing outside? If so, it's probably going to be another 3 to 5 weeks before they start flowering, depending on your location, how much direct sunlight they're getting per day, etc.
But yeah just looking at them, they're definitely still in veg. state, so until they start preflower you won't be able to know for sure.
When they preflower, females will have usually one or two little "hairs" (pistils) protruding from the node. Males generally have 2 or 3 little "balls" form at the node.
Even then sometimes it can be hard to tell from an untrained eye. However, if you start to see exactly what is shown in Stokes' pic above, you know it's male, and those sacks are almost ready to pop, spreading pollen everywhere.
