How to measure muscle growth?

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The vast majority of gym goers train primarily for muscle growth. But how do you know if your muscles have actually gotten bigger?

Unfortunately, there is no conclusive measurement method for muscle growth. However, there are five indicators based on which you can determine with some certainty whether your muscles have grown, provided you use all five (or at least the first four).


As your muscles grow, your body weight will usually increase.

The exception is if your goal is body recomposition, so when you are trying to build muscle and lose fat at the same time. In that case, usually your body weight will remain the same or even decrease, even though your muscles have grown.

Although beginners can ‘recomp’ well, it is much more difficult for intermediate and surely for advanced bodybuilders. They build muscle much more efficiently by handling a small energy surplus, where 10-15% of the maintenance level is usually sufficient. If your maintenance is 2000 kcal, you eat 200-300 kcal on top of that. We also call this ‘bulking‘, although it certainly does not mean that you should eat excessively.

Bulking is not only the most efficient mode for muscle growth, it also makes measuring muscle growth easier. After all, you know for sure that your body weight needs to increase. If that doesn’t happen, no muscle growth has taken place. A possible cause is that in practice you are not in an energy surplus, which is why the use of a calorie app is strongly recommended.

The disadvantage of bulking is that in addition to muscle mass, you will always gain some fat mass. After all, it is impossible to eat exactly as many calories as you need for muscle growth. And unnecessary calories are stored as fat. But if you only use a limited calorie surplus, of 10-15%, the increase in fat mass will remain limited. If you gain a lot of weight in a short period of time, it means you are eating too much.


How much should you gain then, as a sign that you are achieving maximum muscle growth with minimal increase in fat mass? That depends on your training status. Absolute beginners can gain 1 kilo of muscle mass per month, advanced users can often be happy with an ounce. On average, during a bulk with a calorie surplus of ~15% you should see a weekly weight gain of 0.5% of your body weight, including the small increase in fat mass.

By training status:

  • beginners: 0.5 – 1% per week
  • averages: 0.2 – 0.5% per week
  • advanced: max. ~0.2% per week

These numbers obviously apply to natural bodybuilders, who simply have a limited muscle growth potential.


A few more tips for a true measurement of your body weight:

  • Weigh every day (or at least 3-4 times a week) and record the weight;
  • Always do this under the same conditions – preferably in the morning after the first toilet visit;
  • At the end of the week you calculate the average.


A second important indicator of muscle growth is your performance in the gym, which you should therefore accurately record in a training log. After all, for muscle growth it is the intention that you make progress in weight and/or number of repetitions over time: progressive overload.

So do not train purely on feeling and memory. In any case, write down the training weight, the number of sets, the number of repetitions per set and, if necessary, the number of Reps In Reserve (RIR) per exercise .

If the numbers go up in the long run, you’ve gotten stronger, and that’s at least in part a result of muscle growth (assuming you’re training bodybuilding style).

However, the relationship between strength gains and muscle gains is not completely one-to-one. When you do a new exercise, you may initially get stronger at it mainly through neural adaptations (adjustments in the central nervous system) rather than through muscle growth. More on that in this article.


Your reflection in the mirror also tells you something about your progression, although the differences from week to week are usually quite subtle. Your gains are usually only visible in the longer term.

To properly assess them visually, it is best to take progress photos. Make sure you always make them under the same conditions:

  • same place;
  • same time;
  • same exposure;
  • same attitude;
  • same diet.


Of course you can also take the measuring tape in hand and measure the circumference of, for example, your upper arms, thighs and calves at regular intervals.

Unfortunately, that is not really accurate either, because circumference does not distinguish between muscle and fat tissue. You must therefore link the figures of a ribbon measurement to the information that the other indicators give you. If you gain a lot of weight in a short time, the circumference of your legs will also increase quickly, but certainly not only due to an increase in muscle mass.

In addition, it is recommended to buy a real circumference meter. It has a self-tensioner, so you can measure more accurately than when you tension a tape measure yourself.

With a tape measure or circumference meter you can of course also measure your abdominal circumference, which gives a good indication of how much fat mass has been added. Always measure at the same time, preferably in the morning after your first toilet visit.


The best indicator for muscle growth is the development of your fat percentage in combination with that of your body weight. As long as you gain weight slowly during bulking (see point 1) while your fat percentage barely increases, you are on the right track. After all, it means that the increase in your body weight is mainly the result of muscle growth.

There are several methods to measure your body fat percentage:

  • DEXA scan;
  • skinfold measurement;
  • BIA (Bioelectric Impedance Analysis);
  • tape measure (measure the circumference at several points);
  • underwater weighing;
  • CAT scan;
  • MRI scan.

Unfortunately, not all of these methods are equally accurate, including the BIA measurement on modern scales. For a somewhat reliable measurement, you should therefore have a DEXA scan or professional skinfold measurement performed. Something you probably don’t do weekly or monthly, which is why you probably mostly rely on indicators 1 to 4 during the muscle growth process.


Give muscle growth time: bulk for at least two months before starting a cut or maintenance phase. After all, it can sometimes take a while before your nutrition and training are completely on track for optimal muscle growth. It would be a shame to cancel the process after only a month. And with a limited calorie surplus, of 10-15%, you shouldn’t gain too much fat. The little fat that you gain, you quickly cut off later.

Also, do not bulk for too long: on the one hand to keep the increase in fat mass within limits, on the other because your body sometimes also needs training rest, especially if you are more advanced. So keep it to a maximum of six months.

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