1. Estimate resting energy
The Mifflin–St Jeor equation uses weight in kilograms, height in centimeters and age in years. It estimates resting energy expenditure.
| Equation | Calculation |
|---|---|
| Male | 10 × kg + 6.25 × cm − 5 × age + 5 |
| Female | 10 × kg + 6.25 × cm − 5 × age − 161 |
For a 32-year-old woman weighing 68 kg at 165 cm, the estimate is 1,390.25 calories per day at rest.
2. Account for activity and your goal
Multiply resting energy by an activity factor. The site offers factors from 1.2 to 1.9. These are rough categories, not measurements; include activity outside the gym.
Using 1.55 in this example gives about 2,155 calories for maintenance. An illustrative 20% reduction gives about 1,724 calories. The factor and reduction are assumptions for this example, not instructions for everyone.
3. Set protein
Protein provides about 4 calories per gram. If this example uses 136 g protein, it accounts for 544 calories. Choose your own amount using your needs and the daily protein guide.
4. Set fat
Fat provides about 9 calories per gram. Choosing 28% of the example’s calories gives about 483 calories from fat, or roughly 54 g. The adult fat reference range is 20–35% of total energy.
5. Work out the remaining carbs
Subtract protein and fat calories from the total, then divide by 4. Here, (1,724 − 544 − 483) ÷ 4 gives about 174 g carbohydrate.
The rounded example is 1,724 calories, 136 g protein, 54 g fat and 174 g carbs. Rounded grams may add back to a slightly different calorie total. Keep extra precision during calculation, then round the final display.
What if the numbers do not fit?
If protein and fat use more than the whole calorie target, review your assumptions. Do not force negative carbs or an impractically low calorie intake to make a formula work.
Your result is a starting estimate. Compare it with your routine and progress over time; it is not a precise measurement or a promise of a particular outcome.