What is my natural muscular potential? Part 1


In this two-part article I’m going to discuss a question that comes up quite often among weight trainees, that is: what is my genetic muscular potential? Or, in other words, how ‘big’ can someone expect to get naturally (without the use of drugs such as anabolic steroids) with years of training under their belt.

The point of this article is not to appear negative and state what someone will or will not achieve, rather, it aims to provide a realistic expectation of what actually is achievable without the use of drugs. You only need to look at men’s health or other fitness magazines that make claims like, “gain 20lbs of muscle in two months!”, and other such nonsense like, “you’re not ‘big’ until you’re over 200lbs”. Such claims give trainees hugely unrealistic expectations before they start weight training, and ultimately, those people end up disheartened and frustrated when they aren’t reaching their impossible goals. It’s the equivalent of someone expecting to run a sub 2.5-hour marathon with a couple of years training; not to mention the majority of people aren’t genetically endowed in the first place to ever achieve such a feat.

In fact, it would be pretty much impossible for a natural to reach 200lbs (91 kg) at an appreciable amount of leanness, unless they are really tall (>185 cm). Yet somehow, this mentality seems engraved in a lot of lifters minds, which is further solidified by “apparently” drug-free achievements of athletes and models, as well as notable film star transformations (does the cast of the film ‘300’ ring a bell?).

What I’m trying to get at is the fact that we are led to believe that something is attainable when in fact it often isn’t. You can make the argument that “any physique is achievable as long as you have the right work ethic” or that “film stars have access to the best trainers and nutritionists”. Of course, both statements are utter nonsense. I’d also note that the vast majority of these “celebrity trainers” are shit (for lack of a better term). While it may sound somewhat patronising of me to outline what you may or may not achieve ahead of time, I’m basing my opinions on data collected from hundreds of drug-free bodybuilders; the very people you’d expect to have the greatest natural muscular development! The following paragraphs will briefly outline these data and how such predictions of genetic muscular potential were derived.

The Casey Butt model for maximum muscular development

Casey Butt is a natural bodybuilder and owner of the website weightrainer.net. Casey holds degrees in mathematics and physics as well as a Ph.D. in artificial intelligence; so it’s safe to assume he knows his numbers. Over six years of his training career, he collected the statistics of hundreds of drug-free bodybuilders. From these measurements, he came to the conclusion that height; bone size (namely, the wrist and ankle circumferences) and muscle belly length were the best predictors of an individual’s potential drug-free muscular development. Following this, he developed equations based on height, ankle circumference and wrist circumferences to allow someone to calculate how “jacked” he could potentially get. The culmination of this work, in the form of an e-book, can be bought from his website for those of you with more than a passing interest in the topic.

For those of you who want to calculate your muscular potential right away without sifting through an equation-laden book, there is a calculator on his website in which you can quickly type in your height, wrist and ankle girths and desired body fat percentage.

In table 1, I have used this calculator, along my wrist and ankle measurements (6.7” wrist and 8.25” ankle) to generate muscular potentials for lifters of varying heights and degrees of leanness.

Table 1. Estimated maximum muscular potential using Casey Butt’s model


Lean body mass

Body mass at 5% body fat

Body mass at 10% body fat

Estimated maximal bicep circumference at 8-10% body fat








































As previously stated, these are estimations based on my wrist and ankle girths, and variations in these will alter the predicted numbers. As such, for a more accurate estimation of your muscular potential you can always go and enter your measurements into the online calculator. I’ve also included the estimated bicep measurements since a lot of people tend to have delusions about what realistic measurements are. This has probably due to a combination of people inaccurately measuring their biceps (leaving the tape measure slack) or blatantly exaggerating the size of their arms. The latter factor has certainly been a case among many competitive bodybuilders. I’ve also overheard several gym conversations in which trainees claim that they have 17” "guns", whereas in reality, they were much closer to 14”!

From this table, it is also evident that body masses > 200lbs when extremely lean, are only attainable by very tall individuals. For the majority of people, a lean body mass is excess of 165lbs (75kg) would be extremely visually impressive, even for a drug-fuelled athlete.

It is worth mentioning that Casey intentionally left out some statistical outliers in his analysis that he termed “genetic freaks”. They were left out as “these trainees do not represent a typical level of development even for elite [natural bodybuilding] champions”. Another reason for leaving these statistical outliers out of the original analysis is that the drug-free status of some of these genetic freaks has not been verified, only assumed. And “given the ease at which drug tests can be passed by drug using athletes these days this gives me further reason to be skeptical of some of the natural freaks’ drug free claims”. Therefore, “it cannot be stated strongly enough that it is completely unreasonable for the genetically typical trainee to think that he can reach [the] level of development [of these “genetic freaks”]…. Few world-champion drug-free bodybuilders do so, nor do even the majority of anabolic drug users”.

The Martin Berkhan model for maximum muscular development

Martin Berkhan owns the website leangains.com, and has developed a more simple, yet accurate formula (as verified on his clients), again based on natural bodybuilders at competition leanness (i.e. 4-6% body fat). The formula is as follows:

(Height in centimeters - 100) = Body weight in kg at a shredded state (4-6% body fat).

For example, using an example of someone who is 5’11” (180 cm), body weight at a shredded state = “180” – 100 = 80 kg (176 lbs.). Martin also acknowledges the possibility that many bodybuilders are dehydrated or glycogen depleted to a degree on contest day as a “dry” appearance is desired. Therefore, when the effects of dehydration are accounted for (which equates to roughly a 2% drop in total body weight independent of body composition), the equation becomes “Height in centimeters – 98” when hydrated.

Like table 1, table 2 shows the genetic muscular potentials for lifters of varying heights and degrees of leanness. I’ve used the same heights and body fat percentages as table 1 for comparative reasons.

Table 2. Estimated maximum muscular potential using Martin Berkhan’s model


Lean body mass (+2%



Body mass at 5% (contest condition) body fat (+2%



Body mass at 10% body fat (+2%










69    (70.4)

152   (155)

72.5    (74)

160   (163)

76.6    (78)

169   (172)


73.6    (75)

162   (165)

77.5    (79)

171   (174)

81.7    (83)

180   (183)


78.9 (80.5)

173   (177)

83    (84.7)

183    (186)

87.6    (89)

193   (197)


83.6    (85)

184   (188)

88    (89.8)

194   (197)

92.8 (94.7)

204   (208)

* 2% corrects for the effects of dehydration

Though not identical, the values calculated in table 2 are very similar to that obtained in table 1, especially when corrected for the effects of dehydration. Furthermore, Martin’s formula seems to be more in line with Casey’s predictions at heights of 5’10” and above, with values at 6” and 6’2” being almost identical. Martin Berkhan states that a limitation to his formula is that while it is “very accurate for guys smack dab in the middle of that range (180 cm)…. shorter guys (below 170 cm) seem to skew the formula towards being heavier”. Therefore, for shorter people (<175 cm/ 5’9”) the formula becomes:

Height in centimeters – 98-99 = Body weight in kg at a shredded state (4-6% body fat). (The 2% is also added on to this value). Following this adjustment, and that for the effects of dehydration, predicted values at all heights become extremely similar in both models.

This article is getting pretty lengthy now and I’m not close to finishing, so I’ll have to split it into two parts. In part 2 of “what is my natural muscular potential?” I’ll see how I measure up to both models and talk about limitations to these formulae, as well as giving a brief outline of what it takes for someone to reach their muscular potential.