Step 1: Determine BMR.
I use the Mifflin – St Jeor formula
BMR for men
BMR (metric) = (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) + 5
BMR (imperial) = (4.536 × weight in pounds) + (15.88 × height in inches) – (5 × age) + 5
BMR for women
BMR (metric) = (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) – 161
BMR (imperial) = (4.536 × weight in pounds) + (15.88 × height in inches) – (5 × age) – 161
Step 2: Calculate Activity Level
Once you’ve worked out your BMR, you can calculate your daily calorie requirement by multiplying your BMR by one of the following activity level factors:
If you are sedentary (little or no exercise)
Calories Per Day = BMR x 1.2
If you are lightly active (light exercise or sports 1-3 days/week)
Calories Per Day = BMR x 1.375
If you are moderately active (moderate exercise 3-5 days/week)
Calories Per Day = BMR x 1.55
If you are very active (hard exercise 6-7 days/week)
Calories Per Day = BMR x 1.725
If you are super active (very hard exercise and a physical job)
Calories Per Day = BMR x 1.9
BMR X Activity Level will give you estimated Maintenance Calories. Maintenance calories are the number of calories you need to maintain your weight. Understand this is just an estimate. There are a number of variables to consider that could account for this value being higher or lower.
Step 3: Determine Macros
Multiple overall calories by the percentage you want to come from protein.
Multiple overall calories by the percentage you want to come from fat.
When protein and fat has been determined then the remaining calories are assigned to carbs. The calculation would be Total Calories – (Protein Calories + Fat Calories) = Carb Calories divided by 4.
Determine Macros for Weight Loss
Now that you have decided what your maintenance macros you can decide your deficiency. Typically people choose between a 250-500 calorie deficiency.
To determine your deficiency macros, subtract 250-500 calories from your maintenance calories. Next, follow step 3 above to determine your macro breakdown.