Muscle Gain Calculator

Maximum Natural Muscle Gain Calculator

How much muscle mass can you expect to gain in a year and what is your ultimate maximum natural* weight? Use this muscle gain calculator to find out! Before we talk about how much you can expect to gain in a year, its very important what we specify what we are talking about gaining! Weight? Muscle? Fat? The reason this is so important is that many people who report astronomical gains, are reporting weight gain and not muscle gain. Its easy to gain lots of weight fast, just eat at McDonalds 3x/day but it adds fat and not muscle. The only way to know with any degree of accuracy how much muscle you gained is to measure your body composition using a skinfold caliper and scale, a scale alone will not do it! OK, so having that important technicality out of the way, how much muscle can you expect to gain naturally in a year? Use the below calculator and find out.

Please answer all six questions

Step 1: How Long Seriously Lifting?
Step 2: Enter Your Age
Step 3: Enter Your Nutrition
Step 4: Enter Workout Time
Step 5: Enter Your Genetics
Step 6: Enter Your Height

Your One Year Natural* Muscle Gain Prediction

Your One Year Gain Prediction (natural)
  Imperial Metric
Weight gain from natural teen growth spurt (bones, organs, muscles)

Muscle gain from "newbie effect"

Ordinary muscle gain

Total Yearly Lean Body Mass (LBM) gain




Your Predicted Maximum Natural* Bodyweights

LBM (0% bodyfat) kgs lbs
Max Scale weight at 5% bodyfat kgs lbs
Max scale weight at 10% bodyfat kgs lbs
Max scale weight at 15% bodyfat kgs lbs
Max scale weight at 20% bodyfat kgs lbs

Note: To reach this maximum weight, you will have to have to be strict about your nutrition and be willing to do 5-7 hours of hardcore weight lifting per week.


Some maximum muscle prediction calculators use the correlation of wrist size and ankle size of past bodybuilders to predict the limits of natural muscularity, my approach is different. I use the research published in Clin J Sport Med. 1995 Oct;5(4):223-8 which uses the Fat Free Mass Index (FFMI) to determine the upper bounds on your natural muscularity. Here is the forumula for FFMI:

FFMI = (LeanBodyMass / height^2) + 6.1*(1.8m – height)

where height is in meters and LeanBodyMass is in kilograms. The research found that 26 is the maximum FFMI for natural bodybuilders so substituting 26 for the FFMI and solving for LeanBodyMass gives the following formula for the LeanBody Mass

LeanBodyMass = height^2 * (26 – 6.1*( 1.8m – height))

The above equation gives the maximum natural body mass for a given height. Please note that this is a maximum and very few people can reach the maximum, it takes blessed genetics, good nutrition, and killer workouts to get to the max FFMI of 26.

I have used the research mentioned below to attempt to provide as accurate prediction as is possible but bodybuilding is not an exact science, please read about research and bodybuilding. The above provides a pretty darn good guess but of course, there is a wide variation. I have attempted to take into as many factors as possible into account to give you a good prediction of your yearly LBM gain potential but there is a wide variation. The biggest error in this prediction is with teens because of the incredible unpredictability of the teen growth spurt. Please see the expectation range chart on my bodybuilding expectations page to see the wide variation possible and how my calculator comes up with its predictions. These predictions are based upon the CDC growth rate charts and the research done by Westcott et al. 2009.

What is Natural?

Please note, that this calculator predicts your maximum possible natural weight, key of course is which definition of natural I am using. In the context of this prediction calculator, “natural” means no steroids, no pro-hormone supplements, no hormone replacement therapy, and no testosterone boosters – that is, no products that artificially raise testosterone levels. I realize that this is a very, very loose definition of natural and its one that personally I don’t agree with. If you use every product that GNC has to offer that doesn’t boost testosterone, I would consider you natural and the predictions of this calculator would be applicable to you.