Measuring gains while bulking or cutting

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measuring muscle size

By most methods, its very, very difficult to know if you are gaining muscle mass when you are bulking or cutting becuase when the bodyfat changes, all parts of your body swell or shrink as the fat levels change. You can use strength as a guide but strength is not always proportional to mass gain. So how exactly can you see if you are gaining muscle size while you are bulking or cutting? Its actually very simple and just requires a skinfold caliper and a measuring tape. In this procedure you will not be calculating your bodyfat, that is not important. What we want to know here is if your legs, arms, chest are gaining muscle or losing muscle.

Lets take an example and say you want to know if your leg muscles are getting bigger while you are cutting. If you dont gain any muscle while you are cutting then your quad measurement will decrease but that is because the fat under the skin is disappearing. If you were to gain leg muscle you would never know it because your quad measurement would still get smaller. Here is the simple procedure to actually see changes in muscle size. Although this example is for quads, you could do the same thing for arms, calves, or chest.

  1. Measure the quad circumference with a measuring tape at the largest part of the leg.  Go ahead and mark the position of the measuring tape at three places with a sharpie so you can find the same exact place to measure next week.
  2. Measure skinfold thickness at three places you have marked your leg with the sharpie.   Its really, really important that you measure at the same place each week.

Lets now look at how we are going to turn those measurements into a real, fat-free, leg muscle diameter.


To calculate the actual diameter of the muscle under the layer of fat, use this formula:

actual muscle diameter = (measured circumference / 3.14) – (average skinfold measurement)

Note that when you measure the skinfold thickness, you are actually measuring two fat layers, one on each side on the pinched area. The thickness of the layer of the fat under the skin is actually 1/2 of the skinfold caliper reading. In our case we want to subtract two thickness of the fat, one on each side of the leg so we just subtract two times the fat thickness which happens to equal the skinfold caliper measurement (since it measures two thicknesses of the fat layer).
Lets take an example:

  • quad circumference: 710mm
  • skinfold thickness at three points along quad measurement: 8mm, 10mm, 9mm (average value is 9mm)

Your actual muscle diameter is (710mm/3.14) – 9mm = 217mm