Guide · Health
How Many Calories Do You Actually Need?
The Mifflin-St Jeor equation is the most accurate widely-used formula for estimating calorie needs—but individual variation means you should treat any formula as a starting point, not a fixed prescription.
Calculating BMR with the Mifflin-St Jeor equation
The Mifflin-St Jeor equation is the formula recommended by the Academy of Nutrition and Dietetics for estimating Basal Metabolic Rate (BMR)—the calories burned at rest. It takes into account weight, height, age, and sex:
Men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
Women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
For a 35-year-old woman weighing 65 kg and standing 165 cm tall: BMR = (10 × 65) + (6.25 × 165) − (5 × 35) − 161 = 650 + 1,031.25 − 175 − 161 = 1,345 kcal/day.
To find TDEE (Total Daily Energy Expenditure), multiply BMR by an activity factor: sedentary (desk job, minimal exercise) × 1.2; lightly active (light exercise 1–3 days/week) × 1.375; moderately active (moderate exercise 3–5 days/week) × 1.55; very active (hard exercise 6–7 days/week) × 1.725.
| Activity level | Multiplier | TDEE (maintenance calories) |
|---|---|---|
| Sedentary | ×1.2 | 1,614 kcal/day |
| Lightly active | ×1.375 | 1,850 kcal/day |
| Moderately active | ×1.55 | 2,085 kcal/day |
| Very active | ×1.725 | 2,320 kcal/day |
Setting a calorie target for weight loss
A deficit of approximately 500 kcal per day below TDEE produces around 0.5 kg of weight loss per week, which is a sustainable and clinically recommended rate. The example below shows three scenarios for the same 35-year-old woman targeting 0.5 kg/week loss.
The moderate activity scenario is more sustainable: a 1,585 kcal target is comfortably above the 1,200 kcal minimum threshold and allows a varied diet with adequate protein, fat, and micronutrients. The sedentary scenario at 1,114 kcal is very low and difficult to maintain without hunger and nutritional compromise.
This illustrates an important point: increasing activity is often easier than cutting calories to the same degree. Adding 30 minutes of moderate exercise per day (roughly 250–350 kcal) and cutting 150–250 kcal from food achieves the same 500 kcal daily deficit with a more sustainable eating level.
Macronutrients and the importance of protein
Calories come from three macronutrients: protein and carbohydrates each provide 4 kcal per gram; fat provides 9 kcal per gram. Alcohol provides 7 kcal per gram but has no nutritional value. The ratio of macronutrients matters independently of total calories, particularly during a calorie deficit.
Protein is the most important macronutrient when losing weight. A high protein intake (1.6–2.2 g per kg of bodyweight per day) preserves muscle mass during a calorie deficit, increases satiety, and has the highest thermic effect of food (your body uses more energy to digest protein than carbohydrates or fat). For a 65 kg person, this means 104–143 g of protein per day. In practical terms, this requires a deliberate effort—it is roughly equivalent to 4–5 chicken breasts, or achieved more easily by spreading protein across multiple meals with eggs, dairy, legumes, meat, or fish.
These formulas are estimates accurate to ±10–15% for most people. Actual TDEE varies based on genetics, gut microbiome, non-exercise activity thermogenesis (fidgeting, walking around during the day), and other factors. The most reliable approach is to track your weight daily for two to four weeks at a fixed calorie intake and calculate your actual maintenance level from the trend.
Frequently asked questions
What is BMR and how is it different from TDEE?
BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest just to maintain basic functions: breathing, circulation, organ function, and cell repair. It is the minimum energy your body needs to survive. TDEE (Total Daily Energy Expenditure) is your BMR multiplied by an activity factor that accounts for movement, exercise, and the energy used to digest food (known as the thermic effect of food). TDEE is what you actually burn in a normal day and is the figure you use for setting calorie targets.
How many calories should I eat to lose weight?
A deficit of 500 calories per day below your TDEE produces approximately 0.5 kg (1 lb) of weight loss per week, since 3,500 calories roughly equals 0.45 kg of body fat. This rate is considered sustainable and is recommended by most dietitians. Larger deficits (750–1,000 kcal/day) can accelerate loss but increase the risk of muscle loss, fatigue, and nutritional deficiency. Very low calorie diets below 1,200 kcal for women and 1,500 kcal for men are generally unsustainable and should only be used under medical supervision.
Do I need to count calories to lose weight?
No, but awareness of energy intake helps. Many people successfully lose weight by improving food quality (more protein and vegetables, less ultra-processed food) without explicit calorie counting. However, research consistently shows that people significantly underestimate their calorie intake—sometimes by 40% or more. Even a rough estimate of your daily intake for a few weeks can reveal patterns and help you make better decisions without permanent tracking.
Why does my calorie need change as I lose weight?
As you lose body mass, your BMR falls because there is less tissue to maintain. A lighter body burns fewer calories at rest and during movement. This means a calorie deficit that produced weight loss initially will eventually stop working as your TDEE falls to meet your intake. Recalculate your TDEE every 5–10 kg of weight loss and adjust your target accordingly. This is why the last few kilograms of a diet are always the hardest.