3-6 months is usually a little smaller than 6 months but it depends on the brand. My son is currently wearing 3 month and 3-6 months. I’m waiting a while until I get the 6 month clothes out.

@its.a.bird, thank you. I don’t know why I’m even going through her clothes this late lol I just measured some onesie and they were pretty much the same size but others were bigger I’m gonna wait a little while longer before I put her in six months .