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IIFYM | Calculating Macros

IIFYM | Calculating Macros

IIFYM = If It Fits Your Macros. What IIFYM means is that you can have your cake and eat it too, while simultaneously working towards your body goals. IIFYM is a sustainable diet – something you can do for your entire life. The reason for this is that IIFYM advocates for “moderation” and not discounting food because it is labeled as “bad”. IIFYM combines healthy eating (and by this I mean calorically dense food with nutritional value) with what people term “indulgences” aka pizza, icecream, pancakes, waffles, poptarts, candy, etc. The question, of course, is how.

calculating macros

What is IIFYM?

As it says in the name, IIFYM is centered on macros. Macros stand for macronutrients – carbohydrates, fats, and protein. There is a relationship between grams of a macronutrient and its caloric worth: 1g of carbs = 4 calories, 1g of fat = 9 calories, and 1g of protein = 4 calories. Fats generally take up 20-35% of your calories, protein is determined a number of ways (the RDA for protein is 0.8g/kg x bodyweight in kg, but if you’re an endurance or strength athlete, that number increases to 1-1.6g/kg x bodyweight in kg) and the rest of the calories go to carbohydrates.

calculating macros

Calculating Macros

Let’s do an example. The following calculation is one of many ways to calculate calories. I will explain the steps then show you each step’s calculation. Please note, this is how to calculate calories to maintain weight – additional calculations are required to lose or gain weight.

Terms to know when calculating calories
BMR: Basal Metabolic Rate – how many calories you need to be lying down, not exercising, and just functioning.
Activity: Your own activity level and the calories that requires. Sedentary: sit down most of the day, don’t really workout. Light: workout a few times a week. Moderate: workout everyday. Strenuous: lifting very heavy items for long periods of time everyday.
TEF: Thermic Effect of Food – The amount of calories your body uses to digest food.

calculating macros

There is a bit of math involved, but I hope by breaking it down, your own caloric intake will make more sense.

For Calories
1. Convert your weight in lbs to kgs – Xlbs / 2.2kgs = Ykgs
2. Calculate BMR (choose one, male or female)
a. Males: 1kcal/hr x Y(kgs) x 24hours/day = BMR
b. Females: 0.9kcal/hr x Y(kgs) x 24hours/day = BMR
3. Calculate Activity Level (choose one)
a. Sedentary = 0.3
b. Light = 0.5
c. Moderate = 0.7
d. Strenuous = 1
BMR x (Sed/Light/Mod/Stren) = Activity Calories
4. Calculate TEF – (BMR + Activity) x 0.05 = TEF
5. Calculate calories – BMR + Activity + TEF = Total Calories

Now for the macronutrients..
6. Calculate protein – choose between 0.8-1.6g/kg (A) for amount of protein
a. (A)g/kg x Zkg = Protein in grams (B)
b. (B)g x 4cal/g = Protein in calories
7. Calculate fat – choose between 20-35% (C) for amount of fat calories
a. (C) x Total Calories = Fat calories (D)
b. (D)cal / 9cal/g = Fat in grams
8. Calculate carbs – Calories – Protein Calories – Fat Calories = Carb Calories (E)
a. (E)cal / 4cal/g = Carbs in grams

calculating macros

Let’s do this whole thing with me as the example – the calculated numbers are bolded, so you can see how they are used throughout the calculations. For reference I weigh 110lb, I am a female, my activity level 0.7, I take in 1.6g/kg of protein, and 25% of my calories are from fat.

1) 110lbs / 2.2kg = 50kg
2) 0.9kcal/hr x 50kg x 24hours/day = 1080 calories/day (BMR)
3) 1080 x 0.7 = 756 calories (Activity)
4) (1080 + 756) x 0.05 = 91.8 calories (TEF)
5) 1080 + 756 + 91.8 = 1927.8 total calories (rounded up to 1930 cals)
6) 1.6g/kg x 50kg = 80g protein
a. 80g x 4cal/g = 320 protein calories
7) 0.25 x 1930 = 482.5 fat calories
a. 482.5cals / 9cal/g = 53.6g fat
8) 1930320482.5 = 1207 carb calories
a. 1207cals / 4cal/g = 281.8g carbs

Now I have my total calories (1930 cals/day), the amount of calories per macro (fat 482.5 cals, carbs 1207 cals, and protein 320 cals), and the grams of each macro to take in each day (53.6g fat, 281.8g carbs, and 80g protein).

The food I fill my macros with is up to me – but it’s as important to hit micronutrients as it is macros. It took me a while to figure out that these numbers worked for me – I had to tweak them a lot and reduce and increase protein fats and carbs many times until I found what worked for me. Calculating your own macros is a good starting base, but it’s not magic – you have to tweak to suit your needs.


1) I am not a nutritionist nor do I hold a bachelor’s degree in nutrition, I am just speaking from my own experience paired with what I learned from taking nutrition in college.

2) IIFYM might not work for everyone – it is one of the many dietary options people choose upon embarking on a fitness journey.

3) The calculations provided serve as one example of many ways to calculate calories. It is by no means the most effective way, just one of many.


Our articles should be used for informational and educational purposes only and are not intended to be taken as medical advice. If you’re concerned, consult a health professional before taking dietary supplements or introducing any major changes to your diet.



Writer and expert

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