How much should I be eating?

BMR = Basal Metabolic Rate
The amount of calories your body needs just to survive the day doing absolutely nothing.

Go here  to figure out your BMR

Then calculate your daily calorie needs… 
If you are sedentary (little or no exercise) :
Calorie-Calculation = BMR x 1.2

If you are lightly active (light exercise/sports 1-3 days/week) : Calorie-Calculation = BMR x 1.375

If you are moderatetely active (moderate exercise/sports 3-5 days/week) : Calorie-Calculation = BMR x 1.55

If you are very active (hard exercise/sports 6-7 days a week) : Calorie-Calculation = BMR x 1.725

If you are extra active (very hard exercise/sports & physical job or 2x training) : Calorie-Calculation = BMR x 1.9

Once you know the number of calories needed to maintain your weight, you can easily calculate the number of calories you need to eat in order to gain or lose weight.
Lose weight
Gain Weight 

How much weight should you lose? Calculate your BMI here to find out what a healthy weight range is for you. Please keep in mind that depending on your fat/muscle ratio, bone density and a number of other factors the BMI scores are not always 100% accurate. They are a great indicator though.

When you exercise, you will burn extra calories. It can be hard to count how many you have burned but for the most part you can find information online, if you’re on a treadmill or other gym equipment, quite often you can enter your weight etc and it will count for you. There is also something you buy that will calculate calories burned but I don’t think that is necessary for you at this stage. If you’re unsure about how many cals you’ve burned, take a slightly lower quesstimate and go with that :)

NEVER!!!!!! Go below 1200 calories per day. This is just asking for trouble. It will be tempting sometimes, especially as you hit plateaus or have average weeks. But trust me, it is 100% not worth it.

If you stagger your calories throughout the course of the week, your body won’t get used to eating the same amount of food every day and it will help you avoid plateauing. Here’s an example of how it works for a 13419cals/week diet:

Monday: 1917
Tuesday: 1534
Wednesday: 2300
Thursday: 1917
Friday: 1725
Saturday: 2109
Sunday: 1917

The totally number of cals is still the same, but you’ve upped it on some days and lowered it on others to keep your body working and guessing.

To calculate a stagger for your personal caloric intake, go here