What is BMR - Basal Metabolic Rate

Our bodies constantly burn calories, even when we're doing nothing(YES!Even while sleeping).

That means even if we do nothing all day,we need some calories to maintain our body weight(and to stay alive!).

The total amount of energy we burn when the body is at rest is called "Basal Metabolic Rate".

Related:
How to calculate my BMR

How many calories is the minimum per day

The American College of Sports Medicine (ACSM) suggests that calorie levels should not drop below, 

1200 calories per day for females.
1800 calories per day for males.

What is the ideal BMI?

18.5 to 25 .........................optimal weight
lower than 18.5...................underweight
over 25..............................overweight
over 30..............................obese

How to calculate my BMI?

Your BMI is equal to your weight(in kilograms) divided by height(in meters) squared.


i.e BMI = (your weight)/(your height x your height)


Ex:If your weight is 50kg and your height is 1.5m,


Your BMI =  (50)/(1.5 x 1.5) = 22.22

Too Lazy?Here's a tool to make it easy :

How Many Calories Should I Eat

Someone's daily calorie requirements vary from person to person depending on their age,weight,height,sex etc.Therefore, it is hard to simply give a number.You can find many tools that can estimate your daily calorie needs based on your age,weight,height,sex and activity levels.
Here is a cool tool I found.This tool does not only calculate your daily calorie requirements, but also it can estimate the amount of proteins, carbohydrates and fats you should eat a day to lose weight(or to maintain your current weight or to gain weight, depending on what you choose as your "goal")
Please note that The American College of Sports Medicine (ACSM) suggests that calorie levels should not drop below, 1200 calories per day for females and 1800 calories per day for males.


(These tools can only provide rough estimates and Always consult your physician before starting a diet or fitness regimen).