How long do I have to use the Childrens BMI calculators?

The title is pretty self explanatory, I'd like to think.

For those who do not know, I'm 18, and am technichally an adult. How long do I have to strive to eat 1,500 calories before I can drop down to 1,200 for maintainence? Or how long until I can stop reffering to the external links and rely on the CC calculators instead?

Those calculators work up until you're 21. You're still growing until that age. :]

obody maintains at 1200.  That's an arbitrary number based on a very small woman who is totally sedentary (as in practically bedridden) to get enough nutritients to stay alive.  You need to use a calorie calculator appropriate to your age to determine your needs.  I guarantee it will be more than 1200. 

Wait...so I'm supposed to be eating no less than 1500 calories a day? Hmm...definitely was not aware of that. Am I really still growing? Because, um, that'd be awesome (as long as it's up and not out). I'm 20 (in like 2 days) and eating around 1300 every day. So is that bad?