In order to lose weight you have to eat less calories than you burn off. Sounds simple enough. So how do you do it?
First step is to figure out how many calories your burning each day, this is usually described as your Resting metabolic Rate or RMR for short.
Your RMR is the total calories your body will burn today if you don't do any extra exercise or move much at all.
If you browse the web you'll find lots of metabolism calculators online. They typically require you to enter your height and weight, and many of them also require various measurements like wrist, waist or forearms as well.
These calculators are decent and can give you a rough idea of your resting metabolism, however each one has a built in error, so you can never take the number you get as a fact written in stone. Even the best calculators online still only produce an ESTIMATE of your real metabolic rate.
If you want to lose weight but don't know how to start try this:
1) Go online and find at least 3 metabolic rate calculators and get your estimated metabolic rate from each one
3) Use this averaged number of calories as your starting point to test your real daily metabolic rate
4) For 1 week, eat exactly the amount of calories that is stated in step 3 above
The number is correct if you stay the same weight by the end of the week.
If you lose weight by the end of the week then you know this number is too low.
If you gain weight by the end of the week then you know this number is too high.
If you gain or lost weight, try the experiment again for another week and adjust the calories accordingly. Your average number shouldn't be too far off so only adjust by about 200 calories per day.
Keep adjusting in 200 calorie increments until you find the amount of daily calories that keeps your weight the same for a week.
You should be able to find your daily metabolic rate within a month using this system. And this won't be a theoretical number that some calculator told you, this will be the real life number you find by testing your own body.
Once you know this number you will also know that you need to eat some amount below this number to lose weight.
This is the simplest and most effective way to find out how many calories you need in a day.