Calorie Calculator
Daily calorie needs (TDEE), weight goal planning, and exercise calorie burn — using the Mifflin-St Jeor formula
How to Calculate Your Daily Calorie Needs (TDEE)
Your Total Daily Energy Expenditure (TDEE) is the total number of calories your body burns each day accounting for all activity. It's the most important number to know if you want to manage your weight — whether losing, maintaining, or gaining.
This calculator uses the Mifflin-St Jeor equation, which research has consistently shown to be the most accurate formula for estimating Basal Metabolic Rate (BMR) in most adults. Published in 1990, it was derived from a study of 498 subjects and has since been validated extensively.
The Mifflin-St Jeor BMR formula:
- Men: BMR = (10 × weight_kg) + (6.25 × height_cm) − (5 × age) + 5
- Women: BMR = (10 × weight_kg) + (6.25 × height_cm) − (5 × age) − 161
Example: 30-year-old male, 170 lbs (77.1 kg), 5'10" (177.8 cm):
BMR = (10 × 77.1) + (6.25 × 177.8) − (5 × 30) + 5 = 771 + 1,111 − 150 + 5 = 1,737 cal/day
TDEE at moderately active (×1.55) = 1,737 × 1.55 = 2,692 cal/day
To lose 1 lb per week: 2,692 − 500 = 2,192 cal/day. To gain 1 lb/week: 2,692 + 500 = 3,192 cal/day.
Calories for Weight Loss: What the Science Says
The most cited rule in weight management is that 3,500 calories equals approximately 1 lb of fat. This means creating a daily deficit of 500 calories should produce 1 lb of weekly weight loss. While this is a simplified model (actual results vary based on body composition, hormones, and adaptation), it's a reliable starting point for most people.
Safe deficit range: 500–1,000 cal/day below TDEE = 1–2 lbs/week loss. Going beyond 1,000 cal/day deficit is generally not recommended because it increases muscle loss, causes hormonal disruption, slows metabolism through adaptive thermogenesis, and is unsustainable long-term.
Research on very low calorie diets (below 800 cal/day) shows they cause rapid initial weight loss but result in significant muscle loss and metabolic adaptation that makes long-term weight maintenance extremely difficult. The most effective strategy is a moderate deficit with adequate protein intake and resistance training.
Activity Level: How Much Does Exercise Matter?
The difference between a sedentary lifestyle and a very active one can add up to 700–1,000 extra calories burned per day for a typical adult. This difference is bigger than most people realize and is why two people of the same weight can have dramatically different calorie needs.
One factor often overlooked is NEAT — Non-Exercise Activity Thermogenesis. This includes all the calories burned from non-exercise movement: fidgeting, walking to and from places, taking stairs, doing chores, and general daily movement. Studies show NEAT can vary by up to 2,000 cal/day between individuals, making it one of the most powerful determinants of calorie balance. People who naturally tend to fidget or move around often can eat significantly more without gaining weight compared to those who sit still most of the day.
Why Calorie Counting Isn't Perfectly Accurate
Several sources of error affect calorie tracking accuracy:
- Food label errors: The FDA allows up to ±20% error on food nutrition labels. A food labeled as 200 calories could legally contain anywhere from 160 to 240 calories.
- Metabolic individuality: Two people with identical height, weight, age, and activity levels can have BMRs that differ by 10–15% due to genetics, gut microbiome composition, and hormonal differences.
- Adaptive thermogenesis: When you eat less, your body adapts by reducing metabolic rate beyond what's explained by weight loss alone. This adaptation can reduce TDEE by 100–300 calories/day and is a major reason why weight loss slows after several weeks of dieting.
- Cooking methods: Calorie content changes with cooking — raw vs. cooked weights differ significantly for many foods, especially starches and meats.
Despite these limitations, tracking calories consistently — even imperfectly — produces significantly better results than not tracking. Use the calculator's estimates as a starting point, then adjust by ±100–200 calories based on your real-world results over 2–3 weeks.