I want to know how to calculate how much muscle mass one has as opposed actually body fat.

  • 6
    Short answer is that you can't. You can calculate body fat%: fitness.stackexchange.com/questions/262/…. Unfortunately the amount of mass that is not fat is composed of things that do vary such as water weight, amount of undigested food, etc. Commented Jan 16, 2012 at 11:43
  • You may want to post his comment as an answer... even if it is a partial one. Commented Jan 16, 2012 at 16:52

4 Answers 4


When we interview Get Fit Guy, Ben Greenfield for the blog, he mentioned a an ultrasound device which he describes more in his podcast (around the 45-minute mark) with the creator of the BodyMetrix.

Intelamterix makes a product called BodyMetrix that can accurately scan your body fat percentage and track your fat loss and muscle gain. The way the BodyMetrix works is by using ultrasound waves to penetrate the tissue and detect the reflections that occur at different tissues boundaries (such as between fat and bone and bone and muscle). Taking measurements at multiple points of the body can give you and accurate percentage of body fat.

Compared to other methods, the BodyMetrix:

  • Does not require a trained specialist or certified technician to operate
  • Measures consistently regardless of caffeine, alcohol, or hydration levels
  • Is more comfortable than pinching (with calipers), being fully submerged underwater (underwater weighing), or being sealed in a small chamber (air displacement)

The product's faq states:

  • Assessments can take 2-10 minutes
  • Training materials are provided (user's guides, videos, or live web training for Pro users)
  • More accurate than skin fold calipers or bio-electrical impedance devices
  • Results are comparable to underwater weighing and air displacements
  • Non-invasive and portable
  • Safe for children (but not intended for use on children under 6 years)

There are two versions of the BodyMetrix, Personal and Pro. It is quite costly ($495 for the Personal version) and even more so for the Pro version ($1895).

The software itself tracks measurements and can generate reports. Screenshots of measurements and trend from the software (taken from IntelaMetrix's website):

Bodyview 2D body fat measurement screenshot Bodyview 2D weight and body fat % trends

  • I've used one of these, and I've been pretty happy with it. There's still a bit of technique to measuring consistently, but it just takes a bit of practice.
    – G__
    Commented Feb 19, 2012 at 16:26

A low dollar scale on Amazon is the Omron HBF-306C.

I don't work for Amazon, so if you can find it somewhere else I will not be hurt. ;)

Omron HBF-306C

  • fitness.stackexchange.com/questions/262/… NOTE: bio-electric impedance devices are notoriously inaccurate--particularly for athletic people (even with the "Athletic Mode"). Commented Jan 18, 2012 at 20:17
  • 1
    They are more accurate than some high school kid at the gym desk who doesn't know how to correctly measure with skin calipers, and these devices are hundreds of dollars less than installing a hydrostatic water tank to measure body fat. The OP never said he wanted/needed extreme precision.
    – jp2code
    Commented Jan 18, 2012 at 22:39
  • I'm not thinking in terms of raw accuracy. I'm thinking more in terms of consistency. Just a little difference in hydration can have a profound affect on the percentage that the device shows. And that can be affected by how dry the air is in your house, how much you drank (or didn't), etc. Commented Jan 19, 2012 at 14:33
  • @Berin Loritsch, all method of muscle and fat measurement have this exact problem. No one is precise at 100%
    – Ekaen
    Commented Apr 11, 2018 at 19:32

Body fat measurement scales work well enough for your purposes. I've used one for years.

However, I suggest you set yourself up a protocol so that you are consistently measuring. I do it every week, on a Tuesday to allow a day after my last long run on a Sunday. I do it in the morning, before breakfast but after I've used the toilet.

I write the results down in a little notebook and use it to tell me where I am in terms of muscle and fat.

  • Hey Sarge. How exactly does this technique tell you where you are in terms of muscle and fat? I used a technique similar to this years back, and I was unknowingly starving my body and losing muscle tissue.
    – jp2code
    Commented Jan 18, 2012 at 22:42
  • The body fat measurement scales give you body fat as a % and your weight in kg (or lb). Hence, if you see your weight going up you can see if you're adding it as fat or muscle. Vice versa on the way down.
    – Sarge
    Commented Jan 18, 2012 at 23:56

Short answer is that you can't. You can calculate body fat%, unfortunately the amount of mass that is not fat is composed of things that do vary such as water weight, amount of undigested food, etc. Considering even the difficulty in just measuring body fat, you will do good just to keep track of that.

Assuming you keep your diet consistent, you can keep track of weekly changes in lean mass to get an idea of which way things are changing.

A less sophisticated way is to take flexible tape measurements of all your major muscles that you want to track. When things are growing in the right proportions, you are doing well. If not, you'll either need to change your training or your diet.

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