# Better BMI For Tall People and Short People 35

The Body Mass Index (BMI) does not work well for short people nor for tall people. The alternative proposed in this article is the Better Body Mass Index (BBMI). Below is a calculator that demonstrates the BBMI.

 Units: imperial metric Height: Weight: Exponent:

 Underweight BMI (BBMI) <= 18.5 Normal weight BMI (BBMI) = 18.5–24.9 Overweight BMI (BBMI) = 25–29.9 Obesity BMI (BBMI) >= 30

The US National Institutes of Health (NIH) advises that excessive body fat corresponds with a higher risk of various diseases including heart disease, high blood pressure, type 2 diabetes, gallstones, breathing problems, and certain cancers [1]. The NIH suggests using the Body Mass Index (BMI) in combination with the above evaluation table to assess the healthiness of body mass. The metric and imperial versions of the BMI are as follows:

 Metric (kg and m): BMI = Mass ÷ Height2 Imperial (lbs and in): BMI = 703 x Mass ÷ Height2

The formula for the BMI was first conceived by Adolphe Quitelet  (then known as the Quitelet index) and related in such works as, “A Treatise On Man”. The formula became known as the BMI after Ancel Keys’ 1972 publication, “Indices of relative weight and obesity” [2]. Its simplicity was a primary factor in its rise in popularity. Despite this simplicity though, and advancements in computing, it is still used today for such tasks as determining insurance premiums.

A common criticism of the BMI is that it disregards body composition. Muscle is denser than fat, and thus a muscular person may have a misleadingly high BMI despite having a body fat content not unconducive to good health. This short coming limits the usefulness of the index. Another issue is that the BMI is not specific to gender nor ethnicity, despite women generally having a higher body fat percentage and healthy BMI varying between ethnicities (Asians with increased BMI are at greater risk for type 2 diabetes [3]).

For both short and tall people, there is yet another problem, and that is that the relationship between mass and height suggested by the BMI formula may be in error. Though there have been studies finding the implied quadratic relationship [4], there are many that report higher order relationships, as far up as cubic [5]. So while the BMI predicts that humans scale in two dimensions, much like a sheet of paper might, the cubic relationship would imply that humans scale isometrically (proportions are maintained). Yet, taller people tend to appear skinnier than shorter people (proportions are not maintained). It is most likely that humans scale somewhere in between quadratic and cubic, as some studies have found [6].

The Better Body Mass Index (BBMI), proposed in this article, compromises between quadratic and cubic by incorporating a 2.5 exponent in the formula. A correction factor is also applied to ensure that average height people wind up with a BBMI equal to their BMI. The metric and imperial versions of the BBMI are as follows:

 Metric (kg and m): BBMI = 1.3 x Mass ÷ Height2.5 Imperial (lbs and in): BBMI = 917 x Mass ÷ Height2.5

A 2.5 exponent is merely an estimate. The true exponent likely varies for ethnicity, gender, and many other variables. For this reason, the calculator provided at the beginning of this article provides a field for alternate exponents. Note, though, that for whatever exponent is entered for an average height person with a given weight, the reported BBMI remains the same.

By using the BBMI, short and tall people should be less likely to be marked as underweight and overweight, respectively. However, the other issues with strictly mass and height indices remain, such as not accounting for body composition. In reality, such indices are better suited for population studies rather than assessing the healthiness of an individual’s weight. A better alternative for individuals is a fat measuring caliper.

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## 35 thoughts on “Better BMI For Tall People and Short People”

• Kellie

Ok I believe this is getting closer for tall people….now add in bone frame sizing and breast size…I think it’ll be even closer ??

Breast size is mostly fat. If we count breast size, might as well count the fat at your waist.

• Dave

OK, but with the new formula, are shorter people still more likely to have obesity than taller people (in a common population, ethnicity, SES, etc)?

• Tall Life Post author

Depends on the definition I suppose. People do tend to get relatively narrower as they get taller, so I’d personally wager a guess yes.

• Tallboy

I’m on the upper extreme at 6’10. At one point in my life I weighted 210 lbs and I was absolute skeletor. Even the BBMI states that is right in the healthy range. I was completely malnourished and in no way healthy, bar none. My ideal was 270, little muscle but healthy shape and weight and this is considered overweight. Fast forward to the best shape of my life at 330 lbs and that was death defying obesity.

Point and case it still doesn’t apply. According to the scale now I should have died as no human being could possibly weigh as much as I do and love to tell.

• Maari Oldham

I think the range for tall people is too large for normal BMI and this calculator does not fix this problem. I’m tall and have been thin my whole life, I know what a healthy weight is for me. At 5 feet, 11 inches to stay in the normal range I can gain or lose up to 43 pounds. I think this range is too large. I feel fat or too skinny even if I have gained or lost 10 pounds from what I think my ideal weight is.

• Smallish normal

Yes, absolutely, why not?

I am 5ft2 and according to normal BMI measures I am underweight if I drop below 100lbs or so. Yet at my current 98lbs I do not look underweight at all, slim not bony, 30DD bra, 23.5″ waist, periods regular. And no I’m not skinny fat, I’ve got decent muscle mass and low visceral fat. So yes, a 5ft lady could easily be perfectly healthy at 90lbs, especially if she is small framed.

Normal BMI charts definitely underweigh the petite. Apparently I’d not be “overweight” til I reached 135lbs, which is a stretch. The most I’ve ever been is 120lbs and I felt on the curvy side then. I’d consider myself “chubby” (ie slightly overweight) at 125-130lbs

I think that perhaps everyone is so big now that we have lost sight of what “underweight” actually is. Skinny doesn’t necessarily mean underweight or unhealthy.

• Jack

I think the range is too large for any individual person, but a 5’7″, large framed and very muscular woman could conceivably weigh 43 pounds more than a thin and small-framed woman of the same height and they could have similar body fat percentages. Smallish normal says she looks normal at 98 pounds, while I am 5’0 and people thought I looked emaciated at 110 pounds because I have a large frame. 115 – 120 is the ideal range for me personally, even though it might be technically overweight on the short person BMI scale

• AngelKaRa

It makes sense to me. I am 5’10” and I’ve weighed underweight to obese at different stages in life. I think your frame and how you carry your weight, as well as your body composition has a lot to do with it. I’m extra-large frame and I was extremely thin at the low end of normal, but still healthy and looked normal weight at the high end of normal. I believe your bones grow some and widen throughout life too, contrary to common belief and hips certainly widen post-childbirth. At 45 I can’t imagine being as thin as my high school weight. After a decade of health issues, at nearly 55, no one, including my PT and massage therapists can believe I’m 85-100 pounds over weight now. I look Amazonian, but there’s no belly, no back rolls, .. I know I weighed 100 pounds less but my weight is so distributed head to foot, it’s hard to see how it’s possible. I think it’s a matter of scale. My arms and legs are really long. If I look in the mirror, I don’t look obese at all, but put me next to an average size woman and I am just bigger all over. Strangely, I didn’t realize how thin I was before. My massage therapist guessed I needed to lose 20 pounds and was stunned. I know how I looked and felt at different stages. I could lose 50-60 pounds and look curvy, and good, and no one would think of me as overweight if they saw me. Partly, I think I was a lot leaner than I realized to start because I wasn’t taking into account my bone structure. My wrists are 7”. These charts are a starting point, but everyone is unique. And I do think age is a factor as well. As a 16 year old, I weighed 123-128 and wore a size 0-3. In my early 20’s, I ranged 135-150. Still, VERY lean… maybe a size 6-8. By my 30’s-40’s… I settled in around 165-170. Still, no belly, healthy. I have hourglass, so you have to account for breasts and curvy hips, thighs too. I am losing weight now, after many medical issues, surgeries, etc.. but I’m very fortunate that I carry my weight well. I have zero desire to be 150 again. I’m not sure where I’ll land, but I suspect somewhere between 168-207 would work. I might be on the extreme end, but I guess my point is, I do think the talller you are the wider the healthy range.

• Stargate

say i am 6’5″. say i am 209 lbs. I find that to be at 24.8 BMI using the traditional measure (exp of 2). if i then change the exponent to 2.5 and multiply by 1.3 i get 30.16 BBMI. Please explain to me how BBMI is less likely to mark people as overweight who are tall?

• Tall Life Post author

BMI for a 6’5″ person weighing 209 lbs is 24.8. If you change the exponent to 2.5 (BBMI) as opposed to 2 (BMI), then result drops to 23.2, which suggests a healthier wight for that height. Hence the BBMI is less likely to suggest tall slim people to be overweight.

• Me

Wow, with this calculation you’re saying an adult female who is 5 foot could be 90 pounds & a healthy weight, not underweight…. Less than 6.5 stone… I don’t think there are many adults who would be healthy (or having periods) at under 6 1/2 stone…

• Woman

For an incredibly short woman such at that, yes. However, she would be in the absolute bottom of her healthy range, and right on the cusp of being underweight. In my personal opinion, that’s not a goal to strive for. Keep in mind that this is still not an exact measurement, but an improved indication over (traditional) BMI. A good goal for most people would be somewhere in the middle of the “healthy range”, which for her would be closer to 110-115 lbs.

• tomine

I am at that “incredibly short” height of 5 foot. I weigh 52.5 kg, which is in the healthy range of both BMI scales. However, I do have quite a bit of belly fat and slightly too big/fatty thighs and upper arms (but small breasts).

I do not have a particularly narrow frame (rather the contrary!), and in my experience, 48-49 kg is what about right for me. I would think that for more narrow-framed women, an even lower weight (45 kg, for example) could be preferable.

• Too tall

Yet you are ok with the maximum healthy (not beauty contest winning, maximum healthy) weight for a 6’2 / 188 cm is like 193 pounds / 87 kg?

BMI scales incorrectly for height. Tall people have been getting the short end (pun not intended) of the stick.

• Tall Life Post author

People tend not to scale isometrically (proportionally); anthropometric studies show that taller people tend to be relatively narrower and vice versa.

• Jackie

This does not work for me. I am a 4’8 adult female and I was super skinny at 110 lbs. This shows my BBMI was 27, still overweight.

• em

That’s because you would have been carrying excess body fat. 110lbs at your height is too large if you aren’t muscular. My mother at 5’4″ is on the thinner side of healthy at 115lbs, 8 inches taller than you.

• Short woman

Also short woman of 5ft here. And currently 115lbs and i can definitely say I could lose some weight. I feel heavy and tired, sluggish all the symptoms of someone carrying extra weight. I have no idea how you were super skinny at 4ft 8 and 110lbs. Even when i was toned and more muscular i was about 105lbs. Maybe you weighed yourself with a lot of clothes on?

• Anonymous

I’m a 4’8″ adult female too, and I was overweight at 105 lbs and had some chronic health issues. Every photo of me definitely looked much chubbier than women who had a similar, unadjusted BMI of 25. So I lost 20lbs through working out and changing eating habits, and my periods returned, chronic backpain went away, etc. Now I think I look more like women with an unadjusted BMI of 23, so am not definitely not skinny by any means but average. Maybe you have incredibly low bodyfat at the weight of 110. Mine’s 30%.

• JR

• Anonymous

Swear to God at 6’5″ I am almost skin and bone yet the ordinary BMI scale says I am slightly overweight…
I feel really sorry for women over 6′ tall as it is nothing short of insane for them to weigh less than 200lb

• Anonymous

I don’t know if I’d call it insane… certainly slender, but I don’t think it’s unreasonable. I’m a 6’4 fairly athletic man with a slight frame and I only weigh 165lb and I’m in good health.

• Too tall

Yeah but that means you’re in the middle or lower end of the healthy weight for your height. Saying someone 6’2 or 6’5 being overweight from a health perspective at 200 pounds is silly though. It’s certainly at the top (chubbier) range of what’s healthy, but you don’t expect someone at BMI 24.9 to be slender and someone at BMI 25.1 to be a total fat butt.

Again BMI is not a beauty contest or an athletic competition. It’s the range of weights where significant health effects from weight related causes are unlikely (or outside of that range, significantly more likely).

• Elizabeth

uh… no. For a man to be 6’+ and 200lbs is actually a decent sized man, it really just depends how much of that weight is muscle and how much is fat. Women on average have higher body fat percentages than men due to the fact that most men have higher testosterone and androgen production than women, which the body uses as chemical catylists for increased bone and muscle growth. If a woman that would be 20-25% at 200lbs is still expected to be 200lbs to be considered healthy, then that would be a little bit on the extreme side. But more often than not, most women do not have these pretty extreme genetics for this muscle growth, which, by the way, don’t use BMI if you have a ffmi of higher than 22. It’s pointless.

• stickman

This TALL people calculation is better. I am 6′ 9″ and 245 lbs. Using the normal index it says I am (26.3) OVERWEIGHT. B/S. The tall index says I am (23.9) NORMAL. Most of mine friends say I am slightly skinny. One thing that both scales fail to take into fact is the bone structure. I am considered to be large frame so the scale should be adjusted for that.

• Tall Life Post author

Glad you found this one a better BMI. If there was an easy way to account for bone structure, that’d be in the equation too…

• stay slim stay healthy

The new formula is fine Still, most people these days are overweight, so the BMI still is a good reference (and so is the Bbmi…not a lot of difference).

I am 6′ 4″ and run every day 6 km and weigh180, and think that the idea tall people can weigh 200+ is prevalent yet misguided. If you are past 200, your joints are working overtime.

And yes, athletes may have larger muscle mass and weigh more….but the majority of pros today are on steroids and will also develop health issues.

• Just Me

Do you know what is really bad for your joints? Running. If there is one thing that is sure to make your joints work overtime, it’s running.

• Anon

This is definitely better for tall people but still way off for short people. My ex-gf was 4’5″ and 89 lbs. This still shows her as being overweight even though she was so thin as to not be menstruating regularly. I have a friend who is 4’10” and 95 lbs. She doesn’t have an ounce to lose anywhere, but this shows her as being in the middle of the healthy range rather than near underweight.

• Shortish Person

I am 5’5″ & weigh 140. I have unusually broad shoulders & chest, as does my father, with very thick/dense bones. Your scale says I am healthy/normal. Which I feel is true, although I am thin…so thin that if I don’t eat regularly I become tired & weak. My natural weight has always been 150, waist which makes me slightly overweight here & overweight according to regular BMI scales. I felt healthier at 150, I looked better & was much stronger. I could fast for days & not lose strength or mental acuity. It was enough extra that I could suffer an abscess or get really sick & not die. Sure enough I became ill due to Covid & lost 15 lbs in 4 weeks. I am gaining it back, though slowly. If I became ill today I would likely need medical assistance as there’s nothing left to lose. I can see bones, my skin is sagging & breasts are slightly deflated. Your scale does treat me better than most though!
Thank you for developing this formula. Perhaps a section to explain how, when & why the exponent of 2.5 can or should be changed, along with how much it should be adjusted by would be helpful. I see that “frames” are a hard thing to adjust for, but I don’t know why. Thank you again for your time & work, hope you are doing well! – Shortish Person