Our formula for calculating calories uses the Mifflin - St. Jeor formula for basal metabolic rate (BMR) which is considered to be more accurate than the previously used Harris-Benedict Equation.
We start with these formulas:
- Men: (10 * weight in KG) + (6.25 * height in CM) - (5 * age) + 5
- Women: (10 * weight in KG) + (6.25 * height in CM) - (5 * age) - 161
We multiply this value by 1.2 if sedentary, 1.375 if lightly active, 1.55 if moderately active, 1.725 if very active, and 1.9 if extra active.
We then subtract 500 calories per day for every 1 pound of weekly weight loss (3500 calorie deficit = approximately 1 pound of body weight loss).
Next, we take this calorie goal, and use it to arrive at your macros based on your desired ratios.
Example:
Let's say that your calorie goal is 2000 and your desired macros ratios is Ketogenic (5% net carbs, 25% protein, and 70% fat).
2000 calories x 5% = 100 calories from net carbs
2000 calories x 25% = 500 calories from protein
2000 calories x 70% = 1400 calories from fat
Since net carbs and protein are 4 calories per gram, and fat is 9 calories per gram, we can arrive at our macros in grams with this calculation:
100 calories from net carbs divided by 4 = 25g net carbs
500 calories from protein divided by 4 = 125g protein
1400 calories from fat divided by 9 = 156g fat
There you have it -- we've calculated your macros.
This is the same formula we use in the Carb Manager macros calculator.