This is a good general guide, but it's important to know that desis have smaller bones than white people, so they are overweight at lower BMIs and show signs of illness at lower BMIs. So if your BMI is 22, you are not normal, you are likely a bit overweight. Likewise, if it's less than 18.5, don't freak out-it is likely normal in your case. My BMI is 17 which sounds gross, but i'm pretty tuff :P
I don't trust BMI. For example, using this method my cousin and me would come out to be at approximately the same BMI. But our bodies are completely different , he has a lot of fat on him and no muscle mass whatsoever and i have an athletic build(or so i like to think). So in effect its telling me that i am over weight near obese when really i dont think anyone who sees me in real life would ever think that. A better way is to actually go to a place where they will calculate the amount of fat you have on your body and then see where you are at.