How old are they? Since they are still in down I’d think just a few days. It’s really hard to sex most chicks by appearance until they are about 5 weeks old. Even then you can be really unsure with some for much longer. Occasionally you get some that are so obvious that you can tell straight from hatch, especially the males, but not so for the vast majority. Further to LG’s question on the parents, sometimes if you know the color and breed of the parents and which parent is what color, you can tell sex by down color or pattern.
I’ll include a link to a thread that gives some pretty good details of what to look for in trying to sex chicks.
https://www.backyardchickens.com/t/48329/secondary-sex-characteristics
The main clues for me early on are the legs, general posture, and body build. Males typically have heavier legs and a more upright posture. Body build is hard to explain in words, I think that comes more with experience, but more chest typically trends to males. You can read that thread and see all the characteristics they talk about kicking in about 5 weeks. For me that’s often when comb and wattles become really helpful, but chicks with a single comb are often easier that those with other comb types at this age. If you know breed/color some differences in what colors come in where can really help when they feather out.
It’s usually months and not weeks for me when the saddle and hackle feathers become apparent, males have sharp ones, females more rounded ones. A curving tail feather pretty much signifies a male.
For me it’s often easier to say for sure this is a male versus this is definitely a female. There are exceptions, especially with body and head shape and the legs, but some males are such late developers you can be wrong when guessing female. At least I can.
At five weeks if you post photos showing the head for comb and wattle development and a profile showing legs and general body build we can probably come pretty close on most chicks. Until then it is pretty rough.
