It's hard to talk about since ratings are like currency. 100 USD and 100 JYP are very different values. Rating depends not only on the website and rating category, but also the time control. For example 10+0 rapid is not the same as 10+15 rapid... but just like currency, some are nearly the same, and some are wildly different.
Most beginners talk in terms of 10+0 rapid. It's the most played time control, and one that most new players are pretty comfortable with.
For 10+0 rapid on chess.com, I wouldn't be surprised to see a person rated 1600 in one year, but I'd expect them to have played 1000s of games and solved 1000s of puzzles. In other words the hours per day would be high. For someone 21 years old this is certainly possible, but I'd say 2 years or longer is more realistic.
Of all the ratings, OTB (over the board) ratings are the hardest. Even so, starting at 21 is not too late to reach 1600 OTB, but again, I'd expect it to take a few years.
Hey,
I just started to play chess and really got interested and want to know more about the game.
I wonder how hard and how long it will or could take to get to 1600 rating?
Im 21 and just wonder if its too late for me to get to this rating
With kind regards