Rather than relying on online calculators, I think it is worth learning how to calculate macros manually, so you are aware of how it’s done and where the numbers come from.
With iifym, really the most important thing is to pick numbers, and just start. Hit these numbers consistently for at least 3-4 weeks first and from there you will know whether you need to make changes. Having a base to start from, and knowing what happens on these numbers is important. After all it is just guess work for the most part; coaches are using formulas themselves, as well as their knowledge to make educated guesses so having the knowledge around why they are giving you these numbers I think is important. Own your choices, and educate yourself when it comes to your own health; take responsibility.
You must first calculate your BMR (basal metabolic rate), which is the amount of calories you need simply to exist. It does not take in to consideration your NEAT (non exercise activity thermogenesis; the amount of energy you burn during your day to day activities) nor does it include your exercise. It is the bare minimum.
Once you have your BMR, then you add a multiplier for your activity levels which gives you your TDEE (total daily energy expenditure). TDEE is made up of BMR, NEAT and exercise and is the total amount of calories needed to maintain your current state, based on your current activity levels.
Once you have your TDEE, you then decide whether you will be in a deficit (to lose) stay the same (maintain) or be in a surplus (gain/bulk).
Once you have this, then you can calculate macronutrient requirements based on this daily calorie goal.
10x weight (kg) + 6.25x height (cm) – 5x age (years) – 161
10x weight (kg) + 6.25x height (cm) – 5x age (years) + 5
Break it down as follows:
I will use 70kg weight, 178cm height, 32 years age
(10 x 70) + (6.25 x 178) – (5x32) – 161 (or +5 for men)
700 + 1,113 – 160 – 161
1,813 – 160 – 161
1,492 = BMR
To calculate your TDEE, take your BMR and multiply it by one of the activity factors below (or use a number in between two of them if you think this would be more appropriate - again this is educated guesswork, use your best judgement)
Activity Level Description TDEE Multiplier
Sedentary Little/no activity, desk job BMR x 1.2
Lightly Active Light exercise/sport 1-3 days BMR x 1.375
Moderately Active Moderate exercise/sport 3-5 days BMR x 1.55
Very Active Heavy exercise 6-7 days BMR x 1.725
Extremely Active Very heavy exercise/physical job/training 2x/day BMR x 1.9
If I use the very active multiplier of 1.725x it will give me a TDEE of 2,574 calories per day. This amount is what I need to consume in order to cover my BMR, training, NEAT and maintain where I am at currently.
If I wish to lose weight, I need to eat in a deficit. If I wish to gain then I need to eat in a surplus.
For example, if I wish to lose, I could create a deficit and make my daily calorie target around 2,100 – 2,200 calories. Always diet on as many calories as possible; leave room to move should you need it.
Next step is to calculate your macros, and work this in to your current status and body comp goals, and your daily calorie target as above.
First calculate protein, then fats, and the remainder is made up of carbs.
Protein – minimum of 0.8g per lb of bodyweight. If you are to be in a deficit then it is important to have adequate protein to help with muscle retention and satiety. If in a deficit I would suggest around 1-1.1g protein per lb of TARGET bodyweight.
Example, I used my current bodyweight of 70kg if I wanted to drop to say 66kg (145.5lbs) then I multiply by 145.5, I prefer a high protein diet, so I am using 1.1g per lb, which gives me 160g of protein.
Fats – go with 0.4-0.6g per lb of CURRENT bodyweight. 70kg = 154lbs – using 0.4x gives me 62g of fat. I prefer lower fat and higher carb so have used 0.4 multiplier.
Now you have your protein and fat macros, you need to convert this to calories, to then make up the rest with carbs.
1g of protein or carb = 4 calories
1g of fat = 9 calories
160p = 640 calories (160 x 4)
62f = 558 calories (62 x 9)
Total 1,198 calories
If I make my daily calorie target 2,150 calories, then to get carbs I must subtract the fat and protein numbers in calories from the total daily calorie target.
2,150 calories – 1,198 calories = 952 calories left for carbs
952 calories / 4 (carbs = 4 cals per gram) = 238g of carbs
I would make it simpler and go with: 160p 62f 240c
160p = 640 cals
62f = 558 cals
240c = 960 cals
2,158 calories per day
These would be my starting numbers based on my current activity levels, and being in a deficit to lose weight.
Once you have calculated your starting numbers, then hit these for at least 3-4 weeks consistently. Consistency is what gets results, and trusting the process. After this time you will get a feel for how it is working, and can then adjust accordingly. Some people prefer higher fats and lower carbs, and others vice versa. Using the calorie to macro calculations above you can swap fats/carbs around based on what is going to be better for you; at the end of the day it comes down to total calories for weight loss, but for fat loss specifically, and body composition changes then macronutrients are more important. When macronutrients are correct then you have enough energy, hormones should be balanced and you should not get cravings. It can take a bit of trial and error to get just right, but as mentioned, working on getting some numbers to start with can be done with the above calculations - just get started and go with it for at least 3-4 weeks, and from there make adjustments as needed.