We've provided a number of tools you can use on your quest for health.

BMR Calulators

These calculators can be used to help determine your Basal Metabolic Rate (BMR) and your Total Daily Energy Expenditure (TDEE). These numbers in turn can be used to help decide how many calories you should eat in a day to meet your fat loss goals. As a rule of thumb, you should not eat less than your current BMR and a good target deficit might be 15% to 20% less than your TDEE.

The Harris-Benedict formula calculators can be used if you do not know your current body fat percentage. There are separate formulas for men and women, so make sure you select male or female in the calculator.
Harris-Benedict Calculator for Men and Women

If you know your body fat percentage, you can use the Katch-McArdle calculator. Men and women can both use the same calculator in this case.
Katch-Mcardle Calculator for Men and Women

 Also, here is a link to a blog post I wrote on Basal Metabolic Rate and how to use it to determine your daily target calorie intake:
Everyman's Fitness Blog - BMR and TDEE

Body Fat Calculator

We also have a Circumference Body Fat Calculator (Naval Method). The Naval Method uses body circumference, height and weight to estimate body fat percentage. It isn't the most accurate method available, but it is reasonably accurate and it is simple to use. To estimate your body fat percentage you take 2 measurements (if you are a man) and 3 (if you are a woman).
Body Fat Calculator