What Is TDEE and Why Is It the Most Important Number in Nutrition?
Your Total Daily Energy Expenditure (TDEE) is the total number of calories your body burns every single day — from sleeping and breathing to exercising and digesting food. It is the most important number in any weight management plan because weight change is fundamentally driven by the relationship between calories consumed and calories expended. Eat at your TDEE and your weight stays stable. Eat less and you lose weight. Eat more and you gain.
This calculator uses the Mifflin-St Jeor equation, which a 2005 analysis in the Journal of the American Dietetic Association found to be the most accurate BMR formula for the majority of people — within 10% of measured values in most cases.
The Mifflin-St Jeor Equation Explained
For men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
For women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
BMR is then multiplied by an activity factor to get TDEE:
| Activity Level | Description | Multiplier |
|---|---|---|
| Sedentary | Desk job, little or no exercise | × 1.2 |
| Lightly active | Exercise 1–3 days/week | × 1.375 |
| Moderately active | Exercise 3–5 days/week | × 1.55 |
| Very active | Hard exercise 6–7 days/week | × 1.725 |
| Extra active | Physical job + daily training | × 1.9 |
Worked example: 35-year-old woman, 165 cm, 65 kg, moderately active. BMR = (10×65) + (6.25×165) − (5×35) − 161 = 650 + 1031 − 175 − 161 = 1,345 kcal. TDEE = 1,345 × 1.55 = 2,085 kcal/day. To lose 0.5 kg per week, she should target 2,085 − 500 = 1,585 kcal/day.
How to Use Your TDEE for Weight Loss, Maintenance, or Gain
Weight loss: A deficit of 500 kcal/day below TDEE produces approximately 0.45 kg (1 lb) of fat loss per week. This is a sustainable, evidence-backed rate. Do not cut more than 1,000 kcal below TDEE — extreme deficits cause muscle loss, metabolic adaptation, nutrient deficiencies, and are very hard to maintain.
Weight maintenance: Eat at TDEE. Adjust by ±100 kcal if your weight trends up or down over a 2-week period.
Muscle gain: A surplus of 200–300 kcal/day above TDEE combined with progressive resistance training supports lean muscle growth while minimising fat gain.
Why Calorie Counts Are Estimates — And How to Compensate
TDEE calculations are estimates with inherent uncertainty. Food labels are allowed a 20% margin of error. Activity multipliers are averaged from population data. Individual metabolism varies. NEAT (Non-Exercise Activity Thermogenesis — fidgeting, standing, walking around) varies by up to 700 kcal/day between individuals of similar size.
The best approach: use your calculated TDEE as a starting point, track your actual food intake accurately for 2–3 weeks, and then adjust based on what the scale actually does. If you eat 1,800 kcal/day and do not lose weight, your true TDEE is closer to 1,800 than the calculator suggested — adjust accordingly.
Macronutrient Targets from Your Calorie Goal
Once you have your calorie target, divide it into macronutrients. A science-backed starting point:
| Macronutrient | Calories per gram | Recommended % | Example (2,000 kcal) |
|---|---|---|---|
| Protein | 4 kcal/g | 25–35% | 125–175 g |
| Carbohydrates | 4 kcal/g | 40–50% | 200–250 g |
| Fat | 9 kcal/g | 20–30% | 44–67 g |
Prioritise protein — it preserves muscle during weight loss, increases satiety, and has the highest thermic effect (your body burns about 20–30% of protein calories just digesting it).
Frequently Asked Questions
How many calories should I eat to lose weight fast?
Sustainable fat loss occurs at a 500–750 kcal daily deficit, producing 0.45–0.7 kg (1–1.5 lbs) per week. Larger deficits cause muscle loss and metabolic slowdown. The fastest sustainable approach is a 750 kcal deficit with adequate protein (1.6–2.2 g per kg of body weight).
Why is my weight not dropping even though I am eating at a deficit?
Common reasons: water retention masking fat loss (especially early on), inaccurate food tracking (underestimating portions), overestimating activity level, or metabolic adaptation. Weigh yourself at the same time daily for 2 full weeks before drawing conclusions — short-term fluctuations of 1–2 kg are normal.
Does metabolism really slow down when you diet?
Yes — this is called adaptive thermogenesis. Your body reduces TDEE by 5–15% in response to prolonged calorie restriction, making continued weight loss harder. Taking diet breaks (2 weeks at maintenance calories) and preserving muscle through resistance training both help counteract this.
How many calories do I burn walking?
A rough rule of thumb: walking burns about 80–100 calories per mile for a 70 kg person, depending on pace and terrain. A brisk 30-minute walk might burn 150–200 calories. Exercise is important for health but contributes less to weight loss than most people expect — diet drives most of the result.
Are all calories equal for weight loss?
For pure weight change, yes — a calorie deficit leads to weight loss regardless of food source. But different foods affect satiety, muscle retention, hormones, and energy levels very differently. High protein and fibre foods support better outcomes in practice even at the same calorie level.
What is the minimum number of calories I should eat?
Most health authorities recommend no less than 1,200 kcal/day for women and 1,500 kcal/day for men without medical supervision. Below these thresholds, it becomes very difficult to meet micronutrient needs and muscle loss increases significantly.