I use it all the time.
That calculator will tell you the amount of calories needed to stay at your same weight.
Now, If you subtract about 500 calories to that, that is how much you should consume to loose one pound of fat a week.

Now your thinking, Wtf. That isnt Quick. I want it off before school! I want to get into a bathing suit NOW.
Yes, everyone wants their results now, and will be impatient. But for those who stick on slow results, they actually keep it off.
Now this is not from experience, but I have seen a boy that has went from 202 lbs to about 140, average weight, in about a year.
A year is a long time, but it flies by when your getting results. And in that long time you learn how to eat and live right all over again.

A couple of years back I was really overweight and saw an article which said if you want to lose weight quickly avoid these 5 things: Bread, rice, pasta (all kinds), sugar and potatoes. So I ate as much as I wanted but kept off these 5 things. I also started walking 20-30 mins every day (very important – I now try to walk 45 mins everyday). I lost 10kgs (22 pounds) in 5 weeks

Losing weight is one thing, keeping it constant is another. Here’s one tip for you that I learned some time back: one of the signs of dehydration is similar to hunger pangs. So whenever you get hunger pangs, drink water. In fact I drink a lot of water every day. That has helped in keeping my weight constant too.

Lastly, eat small meals more frequently. I try to eat small meals every 3-4 hours.