How Are Calories Calculated? (The Mifflin-St Jeor Guide)
Managing your weight effectively requires moving past "guessing" and using clinical formulas. The Mifflin-St Jeor equation is currently recognized by health professionals as the most reliable way to estimate your daily energy needs.
1. Step One: Calculate Your BMR
Your Basal Metabolic Rate (BMR) is the amount of energy your body requires to keep your heart beating, lungs breathing, and brain functioning while you are at complete rest.
Men :
BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5
Women :
Women: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161
2. Step Two: Calculate Your TDEE
You don't just stay in bed all day. To find your Total Daily Energy Expenditure (TDEE), you must multiply your BMR by an "Activity Factor."
| Activity Level |
Factor |
Description |
| Sedentary |
1.2 |
Little to no exercise, desk job. |
| Lightly Active |
1.375 |
Light exercise 1–3 days/week. |
| Moderately Active |
1.55 |
Moderate exercise 3–5 days/week. |
| Very Active |
1.725 |
Hard exercise 6–7 days/week. |
| Extra Active |
1.9 |
Physical labor or athlete training twice a day. |
3. Setting Your Calorie Deficit Safely
For sustainable fat loss, a deficit of 500–750 calories per day is recommended. This targets a weight loss of 0.5kg to 0.7kg per week, which is much less likely to cause a "rebound" effect than extreme dieting.
⚠️ The Safety Floor: Never drop below 1,200 calories (Women) or 1,500 calories (Men). Consuming too few calories triggers "Adaptive Thermogenesis," where your body slows down its metabolism to survive, making future weight loss much harder.
4. Why "Quality" Still Trumps "Quantity"
While a calorie deficit is required for weight loss, the source of those calories determines your hunger and muscle retention.
- The Thermic Effect of Food (TEF): Your body burns about 20–30% of the calories in protein just to digest it. In contrast, it only burns 0–3% of the calories in fats. This is why high-protein diets are more effective for fat loss.
- Satiety: 200 calories of broccoli is a massive plate of food; 200 calories of soda is just half a can. Whole foods keep you full longer, preventing the "snacking" that ruins most diets.
Frequently Asked Questions
How many calories should I eat per day to lose weight?
Eat 300–500 calories below your TDEE for gradual, sustainable weight loss of 0.25–0.5 kg per week. Avoid cutting more than 1,000 calories below TDEE as it causes muscle loss, fatigue, and metabolic adaptation. A modest deficit sustained over months is more effective than extreme restriction.
What is BMR vs TDEE?
BMR (Basal Metabolic Rate) is the calories your body burns at complete rest — just to keep organs functioning. TDEE (Total Daily Energy Expenditure) includes BMR plus calories burned through activity, digestion (thermic effect), and NEAT (non-exercise activity). TDEE is the number you use for weight management.
How many calories in common Indian foods?
1 medium chapati: ~70 kcal. 1 cup cooked rice: ~200 kcal. 1 cup dal: ~150 kcal. 100g chicken breast: ~165 kcal. 1 medium banana: ~90 kcal. 1 cup full-fat milk: ~150 kcal. 1 tbsp ghee: ~112 kcal.
Does exercise increase calorie needs?
Yes. Exercise increases TDEE, which is why the activity multiplier matters. Running 5 km burns roughly 300–400 calories. Strength training burns 200–400 calories during the session plus additional calories post-workout through muscle repair (EPOC effect). Select the appropriate activity level in the calculator for an accurate estimate.