How Calories Are Calculated
This calculator uses the Mifflin-St Jeor equation, widely considered the most accurate formula for estimating calorie needs.
Mifflin-St Jeor Equation
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
Activity Multipliers
- Sedentary (×1.2): Little to no exercise, desk job
- Light (×1.375): Light exercise 1-3 days/week
- Moderate (×1.55): Moderate exercise 3-5 days/week
- Active (×1.725): Hard exercise 6-7 days/week
- Very Active (×1.9): Very hard exercise, physical job
Calorie Goals
Weight Loss
A 500 calorie deficit per day leads to approximately 1 pound of weight loss per week. The calculator shows a moderate 500-calorie deficit.
Weight Gain
A 500 calorie surplus per day supports muscle gain when combined with resistance training. Larger surpluses may lead to excess fat gain.
Important Considerations
- These are estimates—individual metabolism varies by 10-15%
- Muscle mass increases calorie needs; body fat decreases them
- As you lose weight, recalculate your needs every 10-15 pounds
- Consult a healthcare provider before starting any diet program
Common Food Calorie Reference
- Chicken breast (3 oz cooked): 165 calories
- White rice (1 cup cooked): 200 calories
- Brown rice (1 cup cooked): 218 calories
- Egg (large): 72 calories
- Banana (medium): 105 calories
- Slice of bread: 70-80 calories
- Tablespoon of olive oil: 120 calories
- Apple (medium): 95 calories
Metabolic Adaptation
When you eat in a calorie deficit for extended periods, your body adapts by lowering its metabolic rate — a survival mechanism. This is why weight loss often stalls after several weeks despite the same diet. To counter this:
- Use moderate deficits (500 cal/day) rather than aggressive ones
- Include resistance training to preserve muscle mass
- Consider periodic "diet breaks" (eating at maintenance for 1-2 weeks)
- Recalculate your TDEE as your weight changes
Practical Calorie Tracking
Read the serving size on nutrition labels first — it affects every number on the label. A bag of chips may list 150 calories per serving, but contain 3 servings. Use a food scale for accuracy; volume measurements (cups, tablespoons) can vary by 20% or more depending on how you scoop.