BMI stands for Body Mass Index. The American Council of Exercise defines this as “a relative measure of body height to body weight for determining degree of obesity”. As you can see from the term relative, BMI estimates fat (but does not decipher between someone who is over fat, or someone who is athletic with a lot of muscle) so if you are an athlete and you are unhappy with your number, be sure to use an alternate body composition assessment at your local gym! For the rest of us non-athletes, let’s get an estimate as to where we stand. I will use my own measurements for this example. (Please note that I have seen other formulas for calculating this, but for this example, I will be using the one the American Council of Exercise recommends.)
Don’t be afraid of all of the math you see below. The basic formula is actually simple.
The first thing you need to do is convert your weight to kg. This one is simple. Divide your total weight (mine is 126) by 2.2.
Next we need to convert our height from inches to centimeters to meters. To do this, we need to multiply by 2.54 and divide by 100. I am 5’10, so I am 70 inches tall (5×12=60+10=70).
Now we plug our numbers back into the original formula and viola!
Trust me, I am NOT a math person but this formula really is do-able! 
So now we have this number and we have NO idea what it means. According to our buddies over at the American Council of Exercise, people in a normal weight range have a BMI between 18.5 – 24.9. They define over weight as a BMI between 25.0 – 29.9, and define those obese with a BMI of 30.0 or above.
These numbers are NOT meant to scare you, but to make you aware. I know I am underweight (I can see that when I look in the mirror), but I am happy knowing I am not THAT underweight, and hopefully as I continue to build muscle and bulk up, my BMI will fit into the normal category.
I hope this helped any of you unsure about what a BMI is or how you find it. Have you calculated your BMI? How do you feel about it or the formula in general?
Jennifer is a 27 year old personal trainer living in Connecticut. She is "Coach Jen" at 
{ 18 comments… read them below or add one }
Twitter: JoannaSutter
June 21, 2010 at 9:06 am
BMI gets mixed reviews, doesn’t it? I think you hit the nail on the head…it’s good for awareness!
My BMI has always fallen into the normal range, which includes a very wide range of weights. That has always made me question how helpful it can be. I would much rather calculate and monitor my body percentage…if you know any tips for measuring that, outside of fancy equipment, I would love to hear!
Oh my I am so bad with numbers!! Numbers make my head soin, thank god for my fiance who is great at math, he always hepls Anthony with math homework! lol!!
I have never known my BMI and would be interested to figure that business out! lol!
Love ya! Happy Monday!
I think BMI is a good measurement but not something to live by. As I was losing my weight, I got really excited as my BMI went down and down from Obese to Overweight, but now I’m ready to be normal already!
Twitter: monique_m07
June 21, 2010 at 11:44 am
So, I have a friend who was a fitness/nutrition major in college. She always tells me NOT to invest any faith in the BMI scale, because it was conceived by a psychologist or something to explain peoples’ behavior based on weight figures.
I’m not sure if that’s true or not, but I buy it. I’d like to know your thoughts on that???
I, personally, hate it because it takes zero consideration into muscle vs. fat weight. I have a scale with BMI calcs on it, similar to the one the doctors use. And they always tell me my ideal BMI is about 21ish? Meaning, I’d have to get up to 140ish lbs. Currently, I’m 5’5″ and 120 give or take. Trust me, I’ve been at 140ish and it’s overweight for me. I don’t buy it……? Even at 120, I feel on the higher average size for my frame. But you know, that’s just me.
I really dislike going about life my weights and measurements. I think it should just be how you feel about yourself
Thanks for the info, though!
Monique´s last [type] ..Weeeeeeeeeeee!
Twitter: suki
June 21, 2010 at 12:29 pm
i cheat and use the calculator online: http://www.nhlbisupport.com/bmi/
i’m underweight according to my bmi, which has been a problem for me since forever. :/ starting to work out, so hopefully the muscle will weigh me down a bit!
suki´s last [type] ..RVA Summer Camp : Summer Log Book
I have a love hate relationship with BMI…I would love to do the water test…
Twitter: pennylaaaane
June 21, 2010 at 1:44 pm
Whenever I was in high school my BMI was obsese. I couldn’t believe it! I knew I was overweight but I didn’t think I looked like an obese person. I kind of take my BMI with a grain of salt anymore. I’m still considered overweight according to my BMI but I know I’m healthier than a lot of my friends with normal BMI’s.
Lexie´s last [type] ..I still have trouble zones…
yes good for awareness like your body fat percentage etc…..
Twitter: amapeli
June 21, 2010 at 3:29 pm
There’s one thing I have a problem with here. Muscle weighs more than fat. A friend of mine is a personal trainer, she is THIN but she weighs 180+lbs. Her bmi cant be measured that way. It says shes over weight when really shes in amazing shape.
As a trainer, I’m not a big fan. I know it’s the industry standard, and I know why. But it’s not a good measure of health, and it doesn’t take into account 90-percent of the other health factors that trainers use to measure fitness levels. Still, there’s not a ton of great options out there that are available and affordable for gyms to use. Science hasn’t caught up yet (at least in the ease and affordable sense.)
Twitter: lauryannraik
June 21, 2010 at 8:17 pm
Ugh, this was the one formula that I actually wasn’t too intimidated over when taking the ACE exam! BMI is great for awareness when you are in the obese range, you’re right on that! However, you can take two girls 5’6 weighing 130 pounds that look COMPLETELY different and at two completely different clothing sizes. It all comes down to body fat percentage! My hubby’s a great example, he weighs 218 at 5’11 has a high BMI, but his body fat is low, and he’s essentially all muscle
Laury @TheFitnessRiot´s last [type] ..Acid/ Alkaline Food Balance
Great post, and great discussion!
Ashley@thehungryscholar´s last [type] ..The Rhetoric of Binge Eating
My BMI has always been in the normal range. I haven’t calculated it in a while though. Thanks for the easy formula! I always thought it was a lot more complicated.
I agree BMI is a good tool for awareness but it’s a pretty flawed tool.
Mary (A Merry Life)´s last [type] ..Gyros, Oreo Donuts, and Zucchini Mozzarella Crisps
I don’t really measure BMI because according to that chart, I’m MORBIDLY obese. It just doesn’t factor in muscle and I have a problem with that.
Great post of BMI! Hope you are having a great summer girl!
erica´s last [type] ..Refreshing Heirloom Tomato Salad
the BMI isn’t good science or statistics and should not be used by the medical profession to beat people down. i work with healthy, fit, active people whose providers make them feel awful because their BMI isn’t within some fairy tale range that a mathematician created.