Clean Bulk vs Dirty Bulk: What’s the Difference?

So your buddy keeps telling you the dirty bulk is where it’s at. 

They say it’s way better than a clean bulk. Huh?

Understanding your buddy’s basic premise isn’t too hard — but believing him is another story. 

I think you’ll agree it’s hard to know what to believe about gym culture and science when so much information comes as anecdotes from one lifter to another.

There are no hard-and-fast rules for dirty and clean bulking. But I’m here to clear up the mysteries about weight gain. As a personal trainer, I’ve explained this distinction countless times to my clients. In this article, I’ll show you the best bulking science and give you some tools (a bulking calculator!) to help you on your fitness journey. 

So let’s cut through the opinions and get to the core definition of bulking. Essentially, bulking refers to an eating pattern in an attempt to gain weight, combined with some level of exercise. The differences come into play whether you’re talking about: 

  • Eating enough to gain weight and muscle efficiently without gaining too much body fat, or 
  • Eating in excess to put on as much muscle mass as possible without being concerned about gaining body fat (which you can deal with later!).

Now, let’s define the terms in greater detail and look at the differences between clean bulk and dirty bulk. 

Clean Bulking: A Few Extra Calories

Clean bulk refers to an eating pattern that includes a small surplus of calories each day, which allows you to gain lean muscle mass efficiently without creating unwanted fat gain at the same time. A calorie surplus is when you consume more calories than you burn in a day through activity and regular living.
This method is typically used by athletes or individuals concerned about how much fat mass they have gained or could potentially gain. For example, some athletes need as much lean muscle as possible for performance — think sprinters, decathletes, or wide receivers in football. Following this clean bulking principle, they can stay leaner throughout their training season and perform optimally on the field.       

Dirty Bulking: Lots of Extra Calories

Dirty bulk refers to the eating pattern meant to put on large amounts of muscle mass aggressively. When on a bulking, the goal is to gain strength and size by eating a large calorie surplus.

With more calories, the dirty-bulk eater won’t miss out on any potential strength gains and will likely gain muscle. The dirty bulk route becomes a popular option because it skips the drawn-out process of learning, experimenting, and tracking to discover what amount of calories gives you the best return. 

However, bulking this way also leads to more weight gain (from body fat) due to the extra caloric content. It’s beneficial for strength athletes and certain roles in team sports, like an offensive lineman in football, but perhaps not the best option for those who go to the gym 3–4 times a week.

Gym Bro (& Sis) Dirty Bulk: Dirty Bulk’s Extra-Dirty Cousin

There’s another category of dirty bulk diet that isn’t always discussed. What I’m calling the gym bro dirty bulk is basically an attempt at dirty bulk but with unhealthy processed foods. For beginners (and those who haven’t read this article), this may be the route they attempt, thinking that “dirty” means “unhealthy” and then using it as an excuse to eat anything and everything. 

The term dirty bulk gets lost in translation quite often, and people end up eating three full meals from McDonald’s for dinner instead of clean options. For them, this “guarantees” that they get enough of a caloric surplus for the day and the desired weight gain.

Despite this being the tastiest-looking cartoon cheeseburger you’ve ever seen, there are health consequences of eating processed foods, especially with the high caloric content.

The standard North American diet basically is a dirty bulking diet — with its cheeseburgers, fries, and processed foods — is full of excess calories, saturated fats, trans fats, added sugars, and sodium.

By dirty bulking with these foods, you risk speeding up the processes that lead to a spectrum of health issues, including fat gain and chronic diseases such as heart disease, hypertension, diabetes and cancer. Those fast food hamburgers may be tasty but proceed with caution.

These eating patterns bring up a couple of important questions, so let’s see what the science says.

Bulking Science

Can you build muscle and lose body fat at the same time?

Potentially, yes. It’s technically called body recomposition and can be possible depending on where you are in your training journey. Your training status, type of exercise, and baseline body composition all affect the magnitude of muscle gained and fat lost. Additionally, sleep status, hormone balance, genetics, and metabolism can also affect how much muscle you gain and fat you lose. 

How much muscle can you gain with a clean bulk versus a dirty bulk?

A 2019 study attempted to look at what the optimal energy surplus would be to maximize muscle growth. 

Bad news: they determined that the science isn’t there yet, and there’s no straight answer, unfortunately. The good news is that you can follow a testing approach until we have a better understanding of all the energy-dependent processes that go into muscle development. 

To test what works best, you should measure your muscular gains and compare them against your caloric intake. The study recommends adding a surplus of ~350 calories to ~475 calories, which would roughly fall under what we’re calling a clean bulk. 

For a dirty bulk, I use the muscle-gaining/bulking recommendations for strength athletes from the international society of sports nutrition. They recommend a whopping 50–80 kcal/kg/day for strength athletes. These athletes participated in intense training 4 days per week, designed to elicit hypertrophy. Interestingly, most of these athletes were unable to consume that amount of food (it’s not easy to consume this many calories).

Here’s a handy bulking calculator that our team built so you can figure out which approach would best suit your fitness goals. 

Clean and Dirty Bulking Calculator





Weekly Activity Level

Eating Pattern

How does all this info look in a real-life example?  

To put this into perspective with an example, it’s time for a bit of math 😡. But don’t worry — this math is built into the calculator above to make things easy. 

Let’s look at an example of a man who is 72 kg (160 lbs), 175 cm (5’9”), and 35 years old (this may or may not be me).

For a man with this build who decides to try dirty bulking, he would figure out his caloric intake range with this equation: 

  • Low end: 72 kg x 50 kcal/kg/day = 3600 kcal
  • High end: 72 kg x 80 kcal/kg/day = 5760 kcal

He would need to consume between 3600 kcal and 5760 kcal per day while performing intense exercise. 

For a clean bulk, the calculations are a bit different.

You start with a common formula used to determine your basal metabolic rate (BMR), which is the Harris-Benedict formula. It’s the formula you would use to figure out how many calories you burn just being alive (not including all the exercise you are doing).

Here are the formulas for both men and women. (Again, these equations are built into the bulking calculator, so don’t worry about doing the math on your own unless you’re into that sort of thing!)


  • BMR = 66.47 + (13.75 x weight in kg) + (5.003 x height in cm) – (6.755 x age)


  • BMR = 65.51 + (9.563 x weight in kg) + (1.850 x height in cm) – (4.676 x age)

So for our imaginary 72 kg man, his BMR calculation would look like this:

BMR = 66.47 + (13.75 x 72) + (5.003 x 175) – (6.755 x 35)

BMR = 66.47 + (987.84) + (875.525) – (236.425)

BMR = 1693.41 kcal

Now you can multiply your BMR by daily activity values to get your active metabolic rate (AMR). This is the number of calories you need to consume to maintain your weight, including your daily activity.

  • Sedentary (little or no exercise): AMR = BMR x 1.2
  • Light activity (exercise 1–3 days/week): AMR = BMR x 1.375
  • Moderate activity (exercise 3–5 days/week): AMR = BMR x 1.55
  • Active (exercise 6–7 days/week): AMR = BMR x 1.725
  • Very active (intense exercise 6–7 days/week): AMR = BMR x 1.9

Let’s look at our 72 kg example again. We’ll assume that our exemplary man exercises 6–7 days per week for both the clean and dirty bulk scenarios. You would calculate his AMR like this:

AMR = 1693.41 kcal x 1.725 

AMR = 2921.12 kcal

So, taking the clean bulk caloric surplus suggestions of ~350 to ~475, our guy could estimate his caloric intake as follows:

Low end: 2921 + 350 = 3271 kcal

High end: 2921 + 475 = 3396 kcal

So, if our example dude sticks within this calorie intake range and works out 6–7 days a week, he would likely gain lean muscle mass without excess fat gain.

As you’ve probably noticed, there’s no optimal solution here. The more calories you consume, the better chance there is of fat gain and muscle gain. On the flip side, the fewer calories you consume in surplus of your active metabolic rate, the higher the chance of gaining some muscle while adding less fat. 

Ultimately, the choice is yours. Consider your fitness goals to help you decide. 

Are you aiming for a toned physique, fitness maintenance, or less fat gain? Then I’d suggest a clean bulk approach. 

Are you aiming for brute strength or bulking up for athletic performance? Dirty bulk might be right for you.

Just remember that each pound of fat you gain with the dirty bulk approach will be challenging to lose.

Testing a Clean or Dirty Bulk

So now that you have chosen to go clean or to go dirty 🙃, how do you go about testing to see your results?

You’ll need a reliable testing protocol that allows you to get measurements quite often and as accurately as possible. Adding layers to your fitness routine is great for understanding your progress, but if it’s super hard, you won’t do it.

For the average person, buying a Tanita scale is one of the best ways to test. It allows you to test your weight, muscle mass, and fat mass. It’s simple to use, and there are many versions of these scales that you can get for around $100 or as low as $15 if you want to ship from another country on Aliexpress. The more advanced versions upload your data daily from the scale to your phone, so you can assess our progress weekly or monthly. 

I like to jump on the Tanita scale for weekly tests as there are so many fluctuations in your body weight and muscle on a daily basis. If I test too often, there’s a risk of false positives that can be confusing to assess. For beginners hyper-focused on each pound, this can be tough to deal with. It’s absolutely normal for weight to fluctuate by a few pounds daily due to something as simple as fluid loss or a bowel movement. 

Your main focus should be your muscle mass progress, as that’s the primary goal of bulking — and hopefully, you will see parallel improvements in your strength in the gym. If you don’t see any improvement in muscle mass after two weeks of bulking and consistent exercise, you can make a minor change to your diet and increase your calorie count by 100–200 calories. You can gradually increase your calorie count into the “dirty bulk” range until you see improvements in strength and muscle.

Final Thoughts

Test and see what works best for your body. The real journey begins when you experiment and track to find out how your body responds. Now, grab your calculations and go have some fun in the gym!

If the clean bulk or dirty bulk intrigues you, our team of premium personal trainers is here to help. Contact us to kickstart your bulking journey with accountability and testing throughout the process. 

Mike Hamlin | Personal Trainer

Personal Trainer

Mike Hamlin | Personal Trainer

Mike has been in the training industry since 2008 and is a Certified Strength and Conditioning Coach through the National Strength and Conditioning Association. His personal training philosophy is anchored in developing an effective mindset: Once you have a solid mental foundation to commit to fitness, you can achieve greater fitness goals. You can learn more about Mike on his training profile.

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