Maximum Genetic Muscular Potential – The Models And Their Limitations

Key points:

  • There are limitations to the maximum drug-free muscular potential models out there.
  • It’s useful to be aware of them, but you shouldn’t necessarily cap yourself at what these calculators would peg you as being capable of achieving.
  • As fun as it would be, it is not possible to simply make a calculation to determine whether someone is ‘roided to the gills or not.

The guy you see below is legendary Korean bodybuilder, Kim Jin Ho. This photo was taken of him at the Bodypower Pro show in Birmingham in May, a qualifier to get into the Mr Olympia competition 212lb division. Mr Olympia is bodybuilding at the highest level. The contestants are not tested for drug use. He is 5’4, and weighed 178lbs on that day. He won.

Is it possible that he is natural?

Muscular bodybuilding posing bicep flex

Four weeks ago when a mutual friend of ours insisted that he was, I scoffed at this idea. – Certain models of maximum muscular potential would suggest is he is significantly over his genetic limit. And though in fairness they weren’t developed for people of his stature (very short), he’s simply too far over it for him being natural to be plausible. Or is it?

I may now have changed my tune.

Why I’m Writing This Article Now

Ken and I have built our Japanese language sister site, AthleteBody.jp, into the most popular fitness information site in Japan. We are highly trusted, but with such a big readership I feel there is a big burden of responsibility on our shoulders to get things right.

It came to my attention recently that I had screwed up – we released a translation of an article on genetic muscular potential that left people open to steroid accusations as we hadn’t discussed the limitations. In honesty, I wasn’t aware of them until recently but I should have been more careful. We fixed the error a couple of weeks back by providing an extensive update, and influential industry friends here kindly shared the shit out of the updated version once again on social media.

Now, when it comes to my English readers I am guilty of linking far too many people to a couple of articles on genetic muscular potential over the years, believing the formulas and calculations discussed within to be the definitive word on the subject of what a drug-free athlete can achieve.

They are not.

There are some historical exceptions and limitations to the models that I’d like to discuss. And we’ll finish with our man Mr Kim as an example.

Maximum Drug-free Genetic Muscular Potential Models

The Models In Question:

Lyle McDonald has made an excellent analysis of both in his own article on genetic potential and pretty much concludes that when glycogen and water weight are taken into account, that they come out at roughly the same level regarding maximum muscular potential. I’m not going to go into more detail on it, you can read that here.

The Berkhan Model Of Maximum Drug-free Genetic Potential

Though I’d highly recommend that you read the article, Martin’s formula for determining the maximum that a drug-free trainee will weigh when in “stage-shredded” condition (i.e. 5-6% body fat) is as follows:

(Height in centimetres – 98-102) = Body weight in kilos.

This is likely to be the formula that my Facebook chum Gregory O’Gallagher, at the ripe old age of 23, has used to conclude that he is, “pretty close to the brink of what is achievable naturally for my height.“. He really needs to reel his neck in (and trust DEXA scans less) as he’s doing himself a grave injustice here by placing limiting beliefs on himself, which is something I’ll come to later.

Anyway, if you’re,

  • 173cm tall (5’8), your stage-shredded maximum will be ~75kg (165lbs).
  • 178cm tall (5’10) your stage-shredded maximum will be ~80kg (176lbs).
  • 183cm tall (6’0) your stage-shredded maximum will be ~85kg (187lbs).
  • 188cm tall (6’2) your stage-shredded maximum will be ~90kg (198lbs).

While this is not a bad rule of thumb for estimating what a seriously hard-working trainee will achieve over a lifetime, it doesn’t take into account the genetically blessed exceptions to the rule. We’ll look at these exceptions now.

Using FFMI To Determine What Can Be Achieved As A Natural Bodybuilder

Eric Helms wrote an excellent guest article for Alan Aragon’s Research Review recently, What can be achieved as a natural bodybuilder? Alan decided that it was such an important piece that he published it for free, and I’d encourage you to read it. (For those that won’t be bothered, from here to the table graphic below is a quick summary.)

Eric writes about some famous research from 1995, that looked at the fat-free mass index (FFMI) of steroid using and non-steroid using bodybuilders.

FFMI = fat-free mass in kg ÷ (height in meters)²

In the research 83 users, 74 nonusers FFMI were calculated and then compared. The average FFMI of the steroid users was ~25, of non-users it was ~22, and on the extreme ends a handful of non-users reached a FFMI of ~25.

To put that into more meaningful figures, the average height of the men in both groups was ~180cm (5’11), average body-fat percentage ~13%. The average weight of the steroid users was 92kg (202.5lbs), vs the non-users which was 82kg (180.5lbs).

The maximum FFMI of the non-user group was 25; for the steroid-using group it was 32.

From this research, it was suggested that the genetic ceiling for a natural trainee was a FFMI of around 25.

Comparison With The Berkhan Model

Here’s how the Berkhan model looks when the predicted figures from his model are converted to FFMI:

  • 173cm (5’8), 75kg (165lbs) @5% = 71.25kg lean mass = 23.8 FFMI
  • 178cm (5’10), 80kg (176lbs) @5% = 76kg lean mass = 24.0 FFMI
  • 183cm (6’0), 85kg (187lbs) @5% = 80.75kg lean mass = 24.1 FFMI
  • 188cm (6’2), ~90kg (198lbs) @5% = 85.5kg lean mass = 24.2 FFMI

We can see that the Berkhan model figures are lower, and the math works out to be ~6.5-8lbs (~3-3.5kg) lower than a FFMI of 25.

Research vs History

Eric then goes on to talk about the FFMI data of the Mr America winners from 1939-1959, spanning a period where steroids were almost certainly not used, to a time when they were, that was also discussed in that study.

Using Table 2 from Kouri et al, high scepticism is indicated by the winners in the green box, while moderate scepticism is indicated by the winners in the orange box. If we accept the 1939-1944 winners as natural, the average FFMI is 24.9, with the highest reported at 27.3. Applying moderate skepticism and accepting the 1939-1953 winners as natural, the average FFMI is 25.6, with the highest reported at 28.0. These means are not much different from the 1939-1959 group mean. In fact, the authors analysed the FFMI’s to determine if they were increasing over time. They noted: “there was no significant trend towards increased FFMI among the Mr. America winners over a 20-year span from 1939 to 1959.” Thus if drug use was occurring, perhaps it wasn’t frequent or effective enough to significantly affect the aggregate FFMI.

Mr America Winner FFMIs - 1939-1959

One thing worth mentioning, as it’s an issue I’m sure people will raise: ‘golden age’ bodybuilders usually carried more fat on stage than guys today (8-10% was more common than the 5-6% we expect now) which means their FFMIs were overstated a bit. On the flip side, awesome leg development wasn’t expected or desirable (compare Arnold’s legs to literally any pro BB today), which probably more than makes up for the difference. (i.e. if those guys were competing today, they’d probably have 3-4kg (~7-9lb) less fat, but at least 3-4kg more muscle on their legs and ass.)

Criticisms of the 25 FFMI Genetic Ceiling

1) There were guys with a FFMI over 25 that were almost certainly not on steroids. You can see from the table, one guy had a FFMI of 27.3, and another with a FFMI of 26.9, and if we lower our scepticism just a bit, we can take it all the way up to 28.

2) If we’re going to take a FFMI of 25 (or even 27.3 or 28) as the absolute limit of what’s attainable naturally, we would also have to assume that the most genetically elite people imaginable are included in that sample, which is not likely. Yes, those guys had physiques that were on par with the top drug-tested bodybuilders today (and some lifters of that era, including 26.9 FFMI Grimek, put up weights that are still very impressive by today’s standards), but lifting and physique sports have grown considerably since the ’40s and ’50s.

There is certainly the possibility that there are some people better suited for gaining muscle mass currently participating in bodybuilding and strength sports now, unless we can be sure that the bodybuilders from the ’30s and ’40s represent the absolute pinnacle of attainable human muscularity. However, the records in every other sport have progressed over time as better genetic specimens have entered the pool of competitors (I’d suggest The Sports Gene by David Epstein for more information), so I’m not sure why we’d assume levels of muscularity in drug-free bodybuilding would be any different.

3) We also have to assume that we’ve made no progress whatsoever in terms of training, nutrition, and supplementation. The cynic in me believes that we really haven’t made that much progress in terms of training for hypertrophy since a) periodization doesn’t seem to play much of a role, and b) the biggest determining factor for muscle growth just seems to be training hard and doing a bunch of hard sets, with other factors playing a much smaller role. Basically, getting big isn’t rocket science – it’s mostly about hard work.

However, I do think we’ve made some progress in terms of nutrition and supplementation. I mean, take something as basic as creatine – those guys didn’t have access to it unless they were eating a lot of raw red meat. Will it make a night-and-day difference? No. But it has been shown to pretty reliably help people gain a little more muscle mass.

Applying the Formula – An Example Case

Kim Jun Ho - Bodypower Pro 2015 Lineup - iPhone Snap

So let’s go back to Mr Kim Jin Ho. He was on stage at 178lbs (~81kg), ~5’4 (163cm) in height.

  • This puts him with a FFMI of 29.5, with an adjusted (for height) FFMI of 28.4, which is just 1.1 points above the biggest of the Mr America Winners of the 1939-1944 (almost certainly steroid-free) period.
  • He is 46, so he has a very long training history, and many years to potentially put on muscle.
  • He had a normal voice, his jaw/forehead looked normal, and he doesn’t have the distended gut. (So, no hallmarks of human growth hormone use.)
  • Shredded, but didn’t have the overpowering traps/delts, and no acne marks on his back. (So, none of those obvious signs of AAS use.)

So is he natural?

Well, I wouldn’t bet my life savings on it, but it’s certainly possible. Regardless, this misses the point of this article…

The Point Of The Article

It’s essential to keep these models and their limitations in mind when you plan your bulk. This helps to ground us in reality rather than fantasy land, ensuring that we don’t fall into the ‘dream bulk’ trap, gain a ton of fat, and waste a lot of time and effort dieting it off again.

The Casey Butt / Berkhan model calculations are probably best described as roughly an average of what’s attainable for most reasonably “blessed” people.

A FFMI of 25 is the number usually thrown around as the upper limit, even for someone with great genetics. But as we’ve seen, there are people who go beyond that.

We know that a FFMI of at least 27.3 is attainable naturally, and in all likelihood, 28.0. Add in some minor advancements in training, nutrition, and supplementation, along with some scepticism about whether the most elite of the elite genetically were competing in bodybuilding in the ’40s, and I think it’s pretty likely that some people can attain a FFMI in the 28s naturally. Can many people? Absolutely not. Can most people reach the more conservative limit of 25? Nope. Your genetics are your genetics, and some people were simply dealt a better hand than others. But a FFMI over 25 definitely doesn’t automatically mean someone’s using drugs. And if you have rocketed your way up to the genetic limits calculated by the Berkhan model in your first few years of training, there’s every reason to believe you are one of the few that has the potential to go on and exceed it.

So, don’t limit yourself based on these formulas. The mind exerts a powerful effect over the body. Believe in yourself and have the mindset that you can, and you may just do so.

Update 30th Sept. 2015: Here’s an excellent article by Greg Nuckols over on Strongerbyscience.com on how to calculate YOUR Drug-Free Muscle and Strength Potential.


Thank you for reading. 

Productive discussion, correcting errors in my logic, etc. are welcomed in the comments. Accusations or name calling are not, and will be deleted without hesitation. I just can’t be bothered with it.


Please keep questions on topic, write clearly, concisely, and don't post diet calculations.


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Bro I am a powerlifter and currently 19 years and 184cm. FFMI score is 21.7
Weight- 80kg with 10%b.f. Lifting experience is 2 years.
Bench press – 110kg
Squat- 100kg
Deadlift- 160kg
Question is can I get a 100kg stage ready physique Naturally?
Also what about 200kg bench naturally?? as I never stuck a plateau in any time till now.
What about at men’s physique category Olympia stage?

Adam Yates
Adam Yates

I find this interesting, I scored 28, I’m 1.85m tall and 120kg at 19.7% bf (measured last night with digital calipers). I know I am a genetic freak but I only started lifting again 9-10months ago. I’ve been on and off over the years but I’d argue my genetics are probably better than even Arnold’s. I have 32 inch quads, a 55 inch chest and 19 inch arms completely natural after 10 months. 12 months ago I weighed 25 kilos less. My transformation pics are on Instagram under @adam_yates_physique if it interests any of you. I’m planning on taking this as far as I can and defo got my eye on the prize with pushing my genetic limits. I want to enter the IFBB completely natural and prove everyone wrong that steroids are not the be all and end all of bodybuilding!

Joe Franklin
Joe Franklin

I think the FFMI is really off base. 25 years ago I had an FFMI of 28 completely drug free. My main supplement was peanut butter. I was strong and fairly muscular, but really nothing special. By no means was I gifted. I had friends, who I would estimate would score higher than I did. If you check the scores, the FFMI really goes higher the more you weigh. SO, you can have a really high FFMI with a fairly high fat percentage. For instance someone who is 5 feet 9 inches and weighed 245 with 20% body fat would have a high score.


Hi, I’m 21 years old. 134kg well over weight at 34% bf but my fat free mass is 87.8kg. I am 183cm tall and have managed to increase my fat free mass while dropping body fat. What does this mean as this fat free mass is higher than the examples given? I seem to be able to make fast gains and I am 100% natural (fat is also coming off at a steady pace) will I keep gaining fat free mass or will it stop soon as my bf gets lower? Thank you

Carl Juneau, PhD
Carl Juneau, PhD

Great post! Been a while since I’ve seen anyone add to this discussion in a meaningful way. I’ll share in this week’s bodybuilding science review newsletter.


Hos Delgado
Hos Delgado

Andy, as far as I know, the very first known reference to anabolic steroids in a bodybuilding magazine is dated 1938 – in a magazine called Strength and Health, there is a letter addressed to the editor of Strength and Health. So there is a destinct possibility that in the late 40’s there might have been some experimentation kept strictly between the elite bodybuilders of the time.

Ref: Hoberman JM, Yesalis CE (1995). “The history of synthetic testosterone”. Scientific American 272 (2): 76–81. doi:10.1038/scientificamerican0295-76. PMID 7817189.

Matthias Flehl
Matthias Flehl

Are there studies or better formulas out there related to muscle growth respecting the age?

I mean there should be a tremendious difference in building muscles between a joung boy starting with 15 years and a men starting with 30 or 40 or 60 years when they work out in similar intensity and all other conditions like nutrition, sleep and stress are the same.


I also forgot to give a massive thank you as I was originally 90kg and managed to lose 6kg using your cutting calculator and principles leaned from your site over a 4 month period. (Intermittent fasting and carb cycling). I had the added bonus of some abs for the first time in my life too 😉


I’m sorry but I refuse to believe these figures. I’ve been working out on and off for a few years but only serioisly in the past year. I’m 5’10 and 86kg with about 10% Bf (Jackson pollock method) . I believe I am still a beginner in terms of lifting weight as my squat is only 110kg and benching 90kg on the 5×5 program. I’m still gaining strength and size each month. I have always been a bit heaver than other people my size and build even before starting working out but I have small wrists and ankles and am not big boned. Anyway these calculations mean that I am at the upper end of my limits which is totally ridiculous!


Hi Andy,
Many of the pages I found for adjusted FFMI added a coefficient for height; ie adjusted FFMI = FFMI + 6 x (height – 1.8).

I just had a read of the pubmed extract, and the ratio is REVERSED! 🙂

That is “We then added a slight correction of 6.3 x (1.80 m – height) to normalize these values to the height of a 1.8-m man”.

So the formulae for adjusted FFMI = LBM/(Height^2) + 6.3 x (1.8-Height).

In my case, LBM = 92kg and Height = 1.91m
therefore adjusted FFMI = 92/1.91^2 + 6.3 x (1.8-1.91)
= 24.52

much more reasonable than the suggested 26 which occurred when the coefficient ended up with a positive value adjustment.


Kind Regards,



Trent, in the study text it’s actually 6.1, where the abstract 6.3 (likely a typo). Every online calculator I’ve found appears to get this wrong. Based on how I’m reading the study, the taller people had a higher FFMI, even with less muscle development, so their adjusted formula reduces the number for tall people and increases it for short people. They explain this by pointing out that taller people are usually also wider/thicker, and the standard FFMI formula is 2-dimensional, not 3-dimensional. I’d love to know where all this went wrong. Since most online calculators seem to use the same source code, one mistake seems to have been copied quite a number of times.


Thanks Andy,
I note though, the adjusted FFMI suggests adding to the index for heights above 1.8m.. ie adjusted is FFMI + 6*(height-1.8).. In my case, this takes my current 25 up to 26…

I’ll have a DEXA done in a couple of weeks to make sure my numbers on BF% & LBM are correct… but i’m unlikely to have bf >12%, being i’m only 13 weeks post comp (INBA physique) and haven’t been binging or on a massive surplus….

Has anyone ever calculated a formulae for muscle mass index, ie maximum genetic potential of muscle mass based on height, size, bone density etc?

Perhaps this will be a good question for Eric Helms (he’s co-presenting camps with Layne Norton in Sydney this April, I’m lucky enough to have gotten a place to attend)..

Thanks again.



HI Andy,
Nice article and a good read in the comments too – it’s great to see your engagement with your readers and fans!

Anyway, on the FFMI; is there a way to “adjust for height” for tall blokes?

I’m 191cm, and run a LBM of 92kg at the moment; that’s a FFMI of 25.2..
100% natty, 35 years old and training for only 3 years.

I wouldn’t call myself genetically gifted, growing up as a very skinny, lanky kid & teen.. Whilst my 3 years of lifting has seen me reach half-decent lift 1RM results (Sq 185kg, Dead 245kg, Bench 120kg)..

I still have a good number of years ahead of me and still have room to grow.

I think part of the problem with the formulae is no coefficient for bone density/mass – especially as a taller person further builds on this through compound lifting..

Keep up the great work – btw your page helped me with my first introduction to training back 3 years ago.. Links from Fitocracy brought me to your site, and I used your training recommendations in hand with IF to hit sub 9% for the first time in 2013..


I don’t believe the guy in the example is or could be natural.
All the point made in this article, as well as in the Eric Helms one, is based in the assumption that the FFMI of the Mr Americas is remotley acurate which i don’t think is the case.
Look at the FFMI of John Grimek: it goes from 24 to 26.9 in the timespam of one year. Assuming he is 1,75 tall, he would have gained 9kg (20lbs) of lean mass in that time. 9kg of muscle in one year is a great acomplishment for a begginer, it’s just impossible to put that much in one year (or at all) on top of an already Mr America winning physique.
Also, if you look at photos of these guys, for example Steeve Reeves and Jack Delinger side by side (https://2.bp.blogspot.com/-0ADfy0vRAuI/TpE5sTE9TpI/AAAAAAAADuY/vss7UIDche4/s1600/one.jpg), they look they have the same degree of muscularity. There’s no way one FFMI is 23 and the other 28.
These FFMI of former Mr Americas are completely urreliable to draw any valid conclusion.
A FFMI of 25 is actually great in real life (outside the internet). Its someone with very good genetics who trained hard for years, someone that look big to most people and will be acused of juicing frequently. Most wont reach a FFMI of 25 naturally. There should be some freaks capable of reaching 26, but more than that? I don’t buy into it, specially considering how financially and professionay rewarding is to be a fake natural bodybuilder, trainer or youtuber nowadays.

I agree with Casey Butt when he says : “The truth is 20 pounds of real, permanent muscle would transform your body. Most magazines and websites make it seem like 20 pounds of muscle is nothing …like your grandmother could gain that much. The reality is, if you gain 20 pounds of muscle this year everyone will notice and they’ll probably whisper behind your back that you’re on steroids – my friends did and I didn’t gain nearly that much in any one year. Gain 30 pounds of muscle (above your normal, healthy adult weight) and you’ll be carrying as much muscle as a world-class drug-free bodybuilder.”


Andy, while i don’t agree completely i can see tour points.

You are right about the variability of the conditioning these guys presented at contest day. The carb intake and short use of very high volume in the weeks prior to competition sure could have an effect on lean mass. But 20lbs would be more what a fighter varies in lean mass with weight-in dehydratation. Still possible, just not likely in my opinion.
It’s just that one would expect that the top genetic gifted individuals, with no access to drugs, training with the same goal, would end up somewhat in the same ballpark of muscle mass. But the values vary so much, even in the same individual, that makes me very suspicious of the acuraccy of the measurements. Also because i don’t see that crazy variation in old photos or videos. But i could be wrong.

Let just forget the number aspect for a moment. The old school guys had a very different look, this is not only a matter of body fat percentage, you didn’t see the “full muscle”, “thin skin” pumped look. Look at Clancy Ross: https://www.youtube.com/watch?v=_VCdnLTHSi8. Acording to the chart, his FFMI is over 26, even then doesnt have “that look”.

I agree that there are many individuals that refuse to pull the fake natty routine due to their morals. Unfortunetly these guys are often the guys who have their advice discredited as trainers because they are being compared to drug assisted standards of muscle mass, or are the guys losing a natural bodybuilding competition because they are competing against users.

Just as a closing thought: I live in Brazil, fitness is a big thing here , lots of gyms, so a very large talent pool. But at the same time, while selling steroids is a crime here, the possession is not, and its not as much seem as a morally reproved thing as in some other countries, and even some supplement sponsored competitors admit using. So here people talk more openly about it, and people are more realistic about what can and can’t be achived naturally. Its interesting that here you almost don’t see these huge naturals genetic freaks that appear so frequently in the US.


Hey, sorry for offtopic but could you tell me what comment system are you using? Btw. great blog 🙂


Hi Andy,

I couldn’t find an option to leave a comment for the latest complete diet guide with pdf. Just want to thank you hugely!!
All my friends are abusing printers now to get it on paper:) And this is Super Cool!

Thanks again. Your web site is getting into perfection inevitably:)


P.S. Are you planing to do something similar for the training guide by any chance?


Will do! Please keep us posted when Eric”s text version will come out!
Hope you will be enjoying the rest of the summer!



Andy, thanks for the ideas. I am going to be starting my bulk on August 1, so I will be taking in more food for sure, and will change up my workout to see if I can find something that will work better during this bulk. Since I was on my cut for summer, I have just focused on going heavy, but I think I kept volume to high when I should not have. I guess for me, it just takes about 1.5 – 2 hours of lifting before I start feeling fatigued, or like I am hitting a wall…..


Hey Andy,
So Kim you are saying is natural, even w/ the amt. of definition he has? I mean those quads are insane.

I guess for me, I am just getting to the point where I am disheartened/frustrated.
I am 6’1″ (lanky, very small wrists and ankles), been lifting since I was 17 yrs old, I am 37 now.
I did a lot of basketball, volleyball and stuff in my 20’s and late teens.
And since 2013, I have started IF as well as really giving my workout sessions 100% energy and focus.
But it just seems like I will never get to ~180 lbs, w/ <8% BF
And my high end weight lifting seems to be limited by my joints at this point. Once I start going heavy, then I start feeling it in my joints.

Looking at some posts by Gregory, perhaps I need to back off my workouts some…
He seems to do 3x/week.

Worth a try I guess.


hi andy. just wondered do you just give clients cals and macros to follow or specific meal plans? also still a little confused on progressive overload. if load increases but volume decreases is that overload? many thanks

Da Cruz
Da Cruz

Hey andy. How should my macros look if i choose eating maintence?

If my i need 2k “calories for coma” x the factor ( 1.5 for example ) and also eating 20% plus in the days i train and 20% less in the days i rest. How many protein and fat should i eat? i know the rules for the macros on cutting and bulking but not for maintence.

Can you tell me? and things i’ve said are right?

Thanks and great article!


Awesome work Andy, one of the best articles I’ve read on the topic! In the past I’ve mainly used Casey Butt’s calculator as made some great points in his “Your Muscular Potential” book.

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