29F, I do not want kids. At what point do I tell him?

I am clear I do not want children. Talking to a guy now who seems great. The question tearing me up is timing, when do I drop this. Too early feels heavy for a second call. Too late feels like I wasted everyone months. My mother says do not mention it at all and figure it out later, which I refuse to do. For those who were upfront about being child-free, when and how did you say it? Did it end things instantly?