Flexible Dieting: How to Calculate Your Macros

how to calculate macros

“What are your macros?” This is one of my favorite questions to ask and one of the more common ones I get asked.

Macros, short for macronutrients (proteins, fats, and carbohydrates), form the basis of Flexible Dieting/IIFYM. These macros are the basis of all calories you consume.

Before you read this make sure you’ve read the article What is Flexible Dieting?.

ebooksPlease see our comprehensive guides to flexible dieting/IIFYM. Each edition contains everything you need to know and do to be successful with tracking macros. Plus, meal plans, recipes, helpful hints and much more.
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Calculating and adjusting your daily macro goals is both the bread and butter basics and something you never really graduate from as a Flexible Dieter.

Starting out with Flexible Dieting this seems a lot more complicated than it really is.

Your ability to calculate and adjust your macros correctly will largely determine whether or not you reach your physique goals with Flexible Dieting.

Everybody is different (yes, you are a unique snowflake…) so calculating your macros is just the beginning. And even the most experienced coaches working with clients may get it wrong to start with.

Each person’s metabolism, overall health, and lifestyle all play a vital role in how much energy we actually burn and how much of each macronutrient we should be eating.

But starting with some solid guidelines, even if it isn’t quite right, can be a good start on your journey to dominate your goals, and getting the body you want.

So Where Do You Start?


photo credit: JD Hancock via photopin cc

When getting started with Flexible Dieting the most important thing to calculate is your TDEE (Total Daily Energy Expenditure).

I’ve written more about that here, but basically it’s the amount of calories you burn in a day. Consistently eat less than this and you lose weight or eat more than this and you gain weight.

Please try out our Macro calculator here.

Basic Formula

The Mifflin, M. D., St Jeor formula is one of the most popular and one of the most respected methods used to calculate your TDEE. Here is the formula used to calculate your Resting Energy Expenditure (REE), which is the energy it takes to run your body without any movement.

Here’s what the formula looks like.

For males:

10 x weight (kg) + 6.25 x height (cm) – 5 x age (y) + 5 = REE

For females:

10 x weight (kg) + 6.25 x height (cm) – 5 x age (y) – 161 = REE

Tip: Remember your high school math lesson about Order of Operations: (PEMDAS from left to right) when solving the equation for yourself.

Since most people don’t lie in bed all day doing absolutely nothing, we next have to figure out movement expenditure or TDEE

  • Sedentary
    Just normal everyday activity like a little walking, a couple flights of stairs, eating, talking etc. (REE X 1.2)
  • Light activity
    Any activity that burns an additional 200-400 calories for females or 250-500 calories for males more than your sedentary amount. (REE x 1.375)
  • Moderate activity
    Any activity that burns an additional 400-650 calories for females or 500-800 calories for males more than your sedentary amount. (REE x 1.55)
  • Very Active
    Any activity that burns more than about 650 calories for females or more than 800 calories for males in addition to your sedentary amount. (REE x 1.725)

For those with varied exercise, a more fluid approach can be used. You use your sedentary TDEE as a base and then track your exercise allowing your TDEE to be adjusted based on the amount of exercise you do on a given day. However, this does make tracking your macros a little more difficult. 

A typical TDEE equation could look like this:

Let’s say you’re a 29-year-old, 183 cm, 88 kg, very active male.

Here’s your equation with results rounded to nearest whole number:

(10 x weight (kg) + 6.25 x height (cm) – 5 x age (y) + 5 = REE) x 1.725 = TDEE

10 x 88 + 6.25 x 183 – 5 x 29 + 5 = REE

880 + 1144 – 145 + 5 = 1884 (REE)

1884 x 1.725 = 3250 (Very Active TDEE)

Your TDEE would be around 3,250 Calories.

  • Eat more than this = weight gain.
  • Eat less than this = weight loss.
  • Eat this amount = weight maintenance.

As I mentioned, it’s sometimes not as black and white for all people, but for simplicity’s sake let’s imagine it is.

If you want to lose weight I recommend dropping your overall calories by no more than 20% to start with – So in the example, this would take the guys calories from 3,250 to 2,600 for weight loss.

3,250 – (3250 x .20) = Weight Loss TDEE

If you’re looking to gain weight then add 20% calories to your overall intake. So in the example, this would take the guys calories from 3,250 to 3,900 for weight gain.

3,250 + (3250 x .20) = Weight Gain TDEE

Hate all the math? We do all of this for you with our IIFYM Macro Calculator.

With this knowledge alone you could get started towards your goal. Counting calories can be a very effective way to lose weight (here are some stories of others who’ve done this).

I’ve found losing weight and losing fat can be two different things (you can lose muscle too), hence the importance of measuring each macronutrient.

Basic Formula Exceptions

  1. The Very Lean
    For those with very little body fat and a high proportion of lean body mass, the standard IIFYM formula isn’t best. The standard formula factors in an average body fat percentage, so those with below average will have a lower TDEE calculated with the standard formula than would be typical. Muscle tissue burns more calories even at rest, therefore, should be accounted for. When using our macro calculator, simply use the “Lean Mass” setting. This switches to McArdle, Katch Formula which is the most accurate for those with low body fat.
  2. The Obese
    Just like the very lean, the very heavy have an above average body fat percentage and this also skews the standard formula’s results. Fat tissue isn’t active tissue and requires very little energy to maintain itself. For obese individuals, total fat weight should be considered in the equation. Here’s a more in-depth article that discusses how IIFYM works for obese individuals.

Now Calculate Macros: Protein, Fat, & Carbs

So you’ve got your TDEE sorted. Hi Five! Now let’s figure out the macronutrient ratios that will make up your diet.

Here are the calorie values for each macronutrient:

  • 1g Protein = 4 Calories
  • 1g Carbohydrate = 4 Calories
  • 1g Fat = 9 Calories


First, let’s start with protein. Protein is essential for the growth of new tissue as well as fixing broken tissue – like what happens when you work out. Protein should be your new best friend if you want to gain or maintain muscle.

When lifting heavy and body building, some use a measure of 1 g of protein per pound of bodyweight. However, for most people a more balanced approach is to start with .825 g protein per pound.

So if our individual weighs 195lbs (88 kg), and they are doing a moderate weight training program, then their protein intake will be 161 grams.


Next, let’s calculate fat. Fat has been demonized as the reason most of us are, well, fat. But that’s simply not true.

Fats can be incredibly beneficial for hitting your body composition goals, but they also affect our hormones – too little fat in our diet can be very harmful.

After a bit of research (and again, there are a lot of opinions out there) I designate 25% of overall TDEE calories to fat. This may be adjusted, but this is the starting point.

To figure out 25% of Overall TDEE:
3,250 Calories x 0.25 ( = 812.5 Calories) divided by 9 (9 calories per gram of fat) = 90.27g Fat (which I’d round down to 90 g).


calculate macros

If there’s one thing the Flexible Dieting community of the world agrees on it’s this: We love Carbs!

Think of all your favorite foods and chances are they are high in Carbohydrates. Your body uses carbohydrates to make glucose which is the preferred fuel or energy that our bodies run off of. They’re what keeps us going.

Fiber, which is important to track if you want to be healthy, is also a carbohydrate but doesn’t deliver calories.

We’ve now sorted protein and fats, but how many carbs do we eat? We allocate the rest of our calories (originally calculated from our TDEE) to Carbohydrates.

We started with 3,250 Calories. We allocated 644 calories (161 g) to Protein, 813 calories (90 g) to Fat and we now allocate the rest, 1793 calories, to Carbohydrates.

Since 1g of Carb equals 4 calories we divide 1793 by 4 and get 448 g Carbohydrates.

Final Macros: 161 g Protein, Fat 90 g and 448 g Carbohydrates for this guy to maintain his current weight.

Utterly Confused?

Just go and use our flexible dieting calculator. The calculator allows these variables to be tweaked. We are all individuals and one formula does not suit all.

So How Do I Track My Macros?

1. Use the MyFitnessPal app (iOS or Android)  (Or something similar)

I personally use MyFitnessPal as it has the world’s largest nutritional database. It’s also available across all platforms.

See our tutorial on how to use Flexible Dieting with MyFitnessPal.

2. Buy a Food Scale

A lot of nutritional information is available on food packaging, however, a scale will ensure you accurately track what you eat.

And that’s it. Do the above and you will be well on your way to getting started with Flexible Dieting. As I mentioned the above guidelines aren’t perfect. But it’s a starting place.

So get started and adjust as needed!

Need More Help?



  • Mifflin, M. D., St Jeor, S. T., Hill, L. A., Scott, B. J., Daugherty, S. A., & Koh, Y. O. (1990). A new predictive equation for resting energy expenditure in healthy individuals. The American Journal of Clinical Nutrition, 51 (2), 241-247. URL http://www.ajcn.org/content/51/2/241.abstract
  • Tipton, K., & Wolfe, R. R. (2001). Exercise, protein metabolism, and muscle growth.
  • Fogelholm, M., Anderssen, S., Gunnarsdottir, I., & Lahti-Koski, M. (2012). Dietary macronutrients and food consumption as determinants of long-term weight change in adult populations: a systematic literature review. Food & nutrition research, 56.