Though one of the most popular tools used today to determine whether someone is at a healthy weight or not is the BMI, body fat and lean muscle tissue don’t figure into the equation. This has led many experts to discount BMI as an archaic measurement that isn’t accurate for many people. What is BMI, and why is it a good measure for some, maybe, and completely wrong for others?

BMI, or body mass index, was created in the early 1800s by Adolphe Quetelet. Because of that, it’s sometimes called the Quetelet index. It’s nothing more than a way of comparing a person’s weight to his or her height, and determining if his or her weight falls into a healthy and normal range. The BMI is still used today pretty much as it was when Quetelet invented it.

The formula for figuring BMI (body fat, bone and frame size, muscle and body type aren’t included in that) is this: Take your height in meters squared (your height times itself) and divide your weight in kilograms by that number. For example, if I’m 5 feet tall, that’s about 1.5 meters. To square that number, take 1.5 times 1.5. The result of that is 2.5. So if I weigh 120 pounds, that’s about 54.5 kilograms. Divide 54.5 by 2.5 and I get 21.8 as my BMI. The normal weight range is from 18.5 to 24.9, so 21.8 is classified as a normal weight. Underweight is considered 18.5 and below, while overweight people will calculate a BMI of 25 to 29.9. A BMI of 30 or greater indicates obesity.

BMI, body fat and general health can all be used as signs of how fit a person is. But where general health is pretty self-explanatory and the percentage of body fat clearly shows whether a person gets enough exercise or not, BMI is a bit trickier.

People with a lot of muscle don’t show accurate BMI readings. Because muscle weighs so much heaver than fat but takes up less space, a relatively small statured person can carry a lot of muscle weight without looking huge. BMI doesn’t take that into account. Football players, professional wrestlers, bodybuilders, and virtually any athlete who has a lot of muscle is going to measure as overweight and even obese according to the BMI. So it’s not accurate for them. Is it accurate for everyone else?

The answer to that is yes, and no. It depends on you. The BMI typically doesn’t show an accurate result for children. And extremely tall or large-framed people will show overweight or obese classifications more easily because of the extra weight from their bones and muscles. So for very short, tall or muscular people, the BMI appears to not be a good tool.

There’s also no distinguishing between men and women in the BMI. Body fat is more natural for women who are supposed to have more than men, so some sort of distinction in the measurement of the sexes would help the BMI’s accuracy

A weight loss calculator can be a great motivational tool if you look at it with the right attitude. Whether youve got 10 pounds to lose or 200, punching in the numbers and coming up with goals and time lines can help focus you to the task ahead. In fact, a calculator is just one of the tools you can use to help keep you losing weight and getting healthier without getting burned out or quitting because you dont know what to do next.

The Internet contains every kind of weight loss calculator you can think of. You can calculate your BMI, or body mass index. By entering your height, weight and approximate level of activity, youll get a BMI number. This number determines whether youre about normal, overweight or obese. The lower the number, the better, though it does point out the numbers than mean a person is underweight, too.

The BMI calculator is one of the most common youll find, and one of the easiest to use. While youre losing weight, it can also be fun to punch new numbers into the weight loss calculator from time to time to watch the BMI number go down. Especially satisfying is the day when your number moves from the obese range to the overweight range, or from overweight to normal!

Other types of planning and motivational tools youll find on line are calculators for things like figuring your daily caloric needs. These can be used in a variety of great ways to help you lose weight. First, figuring out how many calories you need a day just to maintain your weight is one of the best things you can do when you plan to drop some pounds. Everyone, whether they want to lose weigh or not, should know about how many calories they should eat in a day, just for general health.

One youve used the weight loss calculator figure your daily calorie needs, if youll subtract 500 from that number and stick to the plan, youll lose on average 1 pound a week. Subtract more calories to lose more, without going below 1500 or 1600 calories. Most people need at least that much for proper nutrition and health. If youre extremely short and small boned you could probably go lower; but not by much. Remember, under eating to lose weight pretty much guarantees youll gain it back as soon as you eat normally again.

Another type of weight loss calculator that can be incredibly motivating can be found online, too. You enter your weight, and your goal weight, and it calculates about how many calories you should eat per day to reach that weight by your specified date. Most will even warn you if your date is too ambitious, and that it would be hard if not impossible to achieve the goal by that date. Some let you enter your goal, and they give you a date. This lets you use a weight loss calculator to plan and monitor your success.