The maximum amount of muscle you can gain depends on your genetics, body type, natural hormone levels, height, bone structure, and how far you are willing to push your training.
This calculator of FFMI (Fat Free Mass Index) is based upon the work of Dr. Casey Butt’s study of pre-steroid era bodybuilding champions.
It is the golden standard for quantifying lean mass, and an FFMI of 26 seems to be the absolute natural limit, and can only be reached by probably less than 1% of the population.
Low lean mass – 16 – 17
Average lean mass – 18 – 20
Muscular – 21 – 23
Pre-steroid era champion bodybuilder (i.e Steve Reeves) – 24 – 26
Note: A person with an FFMI over 26 is highly likely to be a steroid user, or a genetic outlier (“freak”) with one in a million genetics.
Note: The FFMI takes into account lean mass without body fat, so skinny, lean, or fat are not used as descriptors.
You can calculate your FFMI here with a few simple measurements. If you don’t know your bodyfat %, take an educated guess, measure it using a calipers, or use a visual bodyfat chart.
Here is Butt’s very in-depth article on maximum muscular potential. Warning: this article is very science heavy.
Here are my measurements as an example:
Height: 73″ (6’1″)
Body fat: 9% (at around 180 lbs)
Max muscular body weight at 9% body fat: 205 lbs
Measurements at 8% – 10% body fat:
Chest: 47 in
Forearms: 14 in
Legs: 25 in
Arms: 17 in
Neck: 17 in
Calves: 16 in
As you can see, these will give you a goal to work towards, and would be pretty impressive stats for a natural lifter to achieve (in which you would probably have the best physique anywhere you go).
Just for fun, I plugged these numbers (6’1″ height at 205 lbs and 9% body fat) into this FFMI calculator, and came up with an FFMI of about 24 (the low-end of a 1930’s pre-steroid era bodybuilder) with about 186 lbs of lean mass, which is spot on and would be quite realistic given my body type (ectomorphic with slight mesomorphic qualities).
And therein lies the practicality of these calculators: they should give you realistic goals to shoot for. In other words, you will not be 5’9″ 260 lbs at 5% bodyfat like “some” would have you believe without added “assistance”, no matter what promises you’re made.
Is the FFMI the best indicator of progress?
For muscle gain, yes, as it takes fat out of the equation, and a lot of people will just look at the scale for progress while trying to bulk up. Fat is very sneaky, and can accumulate in places you wouldn’t even notice. If you bulk up too fast, most of your weight gained will most likely be body fat. Remember: muscle takes years to build. Fat takes weeks to gain.
The only real problem with FFMI is that fat can sometimes count as lean mass as it does contain water, so those with more fat mass may also measure more lean mass. Also, while cutting, your lean mass will be lower because their will be less water in your muscles, and it will be the opposite while bulking up.
How long will it take to reach my genetic potential?
This depends on many factors, including training intensity and consistency, but a good rule of thumb is around 4-7 years with good nutrition, rest, and training. Good nutrition, rest and training includes strict bodybuilding nutrition (I hope you like chicken, broccoli, and brown rice), 8 hours or more of sleep a night (no partying or staying up late) and 10 hours+ of intense, focused weight training sessions a week (no talking, no phones, and no walking around for long periods looking in the mirrors).
Typical muscle gain for an average to above average lifter:
Year 1: 20 – 30 lbs (noob gains)
Year 2: 10 – 20 lbs
Year 3: 5 – 10 lbs
Year 4: 1 – 5 lbs
Year 5: 1 – 3 lbs
Year 6: 0 – 3 lbs
Year 7: Hit genetic limit, gains stop. Maintenance mode.
As you can see, around 40- 70 lbs of lean mass can be gained over an entire natural lifting career.