Calorie calculators can be found on countless websites. Even Straight Health has its own calorie calculator which uses sex, weight, height, age and activity level to estimate a person's daily calorie expenditure. But are these numbers reliable and should you base your diet off of them?
The answer is a bit more complicated than a simple yes or no. All of these calculators are based off of a formula (the most popular being the Harris-Benedict Formula) that takes into account all of the variables listed above. For example, a 20 year old male that is 5 feet, 10 inches, weighs 160 pounds and exercises moderately (3-5x per week) would burn 2814 calories per day.
If a 20 year old were to start a new diet with the help of one of these calorie calculators, would he need to eat exactly 2814 calories everyday in order to maintain his weight? The answer is no. While these calorie calculators give a good estimation of how much you should eat, they aren't exact. To give a good estimation for most people, these calculators are based on formulas that are very general.
For example if you take two people with all of the same variables except one has a very high body fat percentage and the other is very muscular, though a calorie calculator will give them both the same number, in reality, these two will have a very different daily calorie expenditure. These calculators don't take into account lean muscle mass which can have a big impact on calorie expenditure.
The Bottom Line
The point of these calculators is to give you an estimation of how much you should be eating per day. Start out with that estimation, weigh yourself and adjust your calorie intake accordingly. If you're gaining weight when you think you should be losing weight, lower your calorie intake. If you're losing weight when you think you should be gaining, do the opposite.