Dear Saptarshi Mozumdar,
You are outdoors, and active, and starting a wholesome lifestyle for yourself...and learning to ride a bicycle which will be wonderful for you! And that is a very fine beginning.
At your age of 16, I would like to see you just moving around a lot...walking, gardening, playing, whatever you love for as much as two hours daily, just have fun. That builds your stamina, strengthens your muscles for your whole life to come. In addition, do some exercise that gets your heart rate up for 15 to 30 minutes per day. And then when you can, do go on a longer bike ride or hike with friends, again having fun.
My thinking would be to eat healthy, but not necessarily try to cut your calorie intake really low. In other words, rather than focusing on weight loss to think more of bringing your body into balance; wholesome diet, lots of gentle movement plus some real exercise.
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However, to answer your question I found an online calorie calculator for you. A sixteen year old man 5 feet 8 inches tall, and 227 pounds, with 15 to 30 minutes exercise five days per week, it takes 3,000 calories daily just to maintain your weight. Anything less and you are losing weight. And 1800 calories per day would mean extreme fat loss for you...and I personally think 1800 calories per day is too low for you, I would like to see you eat more than that.
I will leave you the link for the calorie calculator, and I would like to suggest, if you do not mind, that since you are so dedicated why don't you also see a nutritionist? A good one could really help you fine-tune your weight-loss program for good health.
And I wish you all the best, it should be wonderful!
http://www.freedieting.com/tools/calorie_calculator.htm