There are a lot of fairy tales about how many kanji a day is possible to learn and obviously there is a lot of variation between us humans and how much time we can devote each day to learning japanese but for the most part the outrageous claims of learning double digits kanji a day is utter bullshit.
This post is going to come off as sligthly pessimistic but bear with me. I myself know a few houndred but I also discussed with veterans who have passed JLPT N2(they know more than 1000+ kanji) and literally nobody said it was possible to even keep a rate of 10 new kanji a day.
You’re going to read claims on the net of 20, 30, 50 and even 100 kanji a day is possible. If they are selling you a product then run the opposite direction as fast as you can. Japanese seems to be one of those languages that is seriously infested with marketers trying to sell their over hyped teaching products.
Going from my own experience it is actually not that crazy to learn 10 new kanji everyday in the beginning because the first 200-300 kanji are so frequent you will keep seeing those kanji over and over again in context(for example working through a standard textbook like genki or minna no nihongo will expose you to the basic kanji). But you will eventually hit a wall just like I did. It worked fine uptil about 200 kanji then I had to pause in order to go back and review the kanji I kept forgetting, 10 new kanji was already getting too difficult for me to handle and I wasn’t anywhere near 1000 let alone 2000 kanji that is needed for JLPT N1. The typical rate for full time language students is 4 to 6 kanji per weekday. In other words a typical full time language school student wouldn’t even be near 10 kanji per day.
My opinion is in line with japanese language schools, somewhere around 20-40(around 20 is standard) kanji a week is reasonable, in other words about 5 kanji per day is a realistic goal for ambitious students.
3 kanji a day for someone self studying outside Japan who might not be spending a reckless amount of time but still a relatively ambitious student.
But even 1 or 2 kanji per day is not bad. That still 365 or 730 kanji per year. So even at a somewhat slow rate(this is still faster than the typical college course) you could know all the N3 Kanji(roughly 650) in less than a year without pushing yourself too hard.
I wouldn’t say 10 kanji a day is impossible but it requires a lot of devotion and a special kind of person to achieve that and I’m betting that about 99.99% of people aiming for 10 new kanji per day end up failing I’ve yet to meet a person in real life succeding at this and I’m living in Japan studying full time so you understand where my skeptiscism is coming from.
Generally speaking, I’m of the opinion that learning a language is like running a marathon. If you rush it, you will most likely learn slower after everything is said and done than someone who studied at a reasonable pace.