I figured it out on my own when I was about 12. I didn't tell my parents until I was 14, and it was really hard for me (I have trouble communicating to people to begin with...). I also forgive very quickly (one of my biggest flaws at times), so if your daughter isn't quite as forgiving, you might want to tell her instead. I know a couple of 13 year olds who still believe and I know 7 year olds who know, though the majority of people that I know found out when they were about 11 (grade 7).
I also still like to pretend, so if you want to tell her, you could say that it's a game, so she has to pretend that Santa is real, and still do Santa and Tooth fairy and Easter Bunny, except she knows the truth. I think that can take some of the magic out of it, like writing a letter to Santa because what's the point? He's not real, no one's going to read it anyway.
Let them figure it out on their own.
Just prepare a spiel for if they ever ask you about it. Like how Santa Claus was used to keep them well-behaved and be good little boys and girls.
She will figure it out when she's ready. Why end the magic for her before then? I am nearly 70, and I would happily board the Polar Express in a heartbeat. :) LOL
I gave you my thoughts on the subject in a message my friend. ☺
Kids usually find out on their own, usually from kids slightly older when they are around 6 pr 7. But the age does vary.
Our youngest was fairly upset briefly, but they are used to magic coming and going at that age.
The fact that we might occasionally tell them to be good because Santa will know is usually not a problem.
The unconditional love of a mother and the conditional love of a father is the primary way we learn about what's "good" and "bad" anyway---not because Santa has a "list."
I don't think I ever really believed in Santa and I told our daughter the truth. My mother thought I was terrible but as I became more aware of the NAM (New Age Movement) and prayed for an understanding, more things were made available to me about the deception all around us. Whether that's part of the delusion God sends I just don't know but if you remove the "n" from Santa and place it at the end of his name, what does that spell?
Believing in imaginary creatures like Santa, and the Easter Bunny are as harmless as a child's imagination will allow. Children learn from fairy tales and stories all the time. Their imagination helps their brains to develop in a healthy way. Imagination and make believe is what fortifies a childhood.Â
Children are growing up fast enough these days .. too fast it seems  ., and it disturbs me deeply to see the direction it's taking. 8  and 9 year olds dating, the shear number of children engaging in sex, child pregnancies .. THAT is the direction this  world is going thanks to the so called "New Age Movement" .. its sad .. just really really sad.Â
Kids are not allowed to be KIDS!Â
What do you mean Santa's not real 0-0
Okay, but to actually answer your question, they usually figure it out on their own when they're around six or seven or so (that's around the age when my brother and also I found out.)
Though I personally find the custom to convince children of a man who is immortal and breaks into everyone's houses on a certain night every year to be weird. I don't want kids but if I did have them, I would tell them about Santa and stories for fun but wouldn't try to convince them that he actually exists. But I guess it's your choice really.
I would say 10 11 or 12. I was about 12.