TDEE Calculator

How It Works

Total Daily Energy Expenditure is the sum of basal metabolic rate, the thermic effect of food (about 10% of intake), and physical activity energy expenditure. TDEE = BMR x activity factor, where the factors come from doubly-labeled water studies: sedentary 1.2 (desk job, no exercise), lightly active 1.375 (light exercise 1-3 days/week), moderately active 1.55 (moderate exercise 3-5 days), very active 1.725 (hard exercise 6-7 days), extra active 1.9 (physical job plus daily training). The Mifflin-St Jeor BMR equation, validated by the Academy of Nutrition and Dietetics in 2005 against indirect calorimetry, predicts measured BMR within 10% for 80% of normal-weight and overweight adults, outperforming both Harris-Benedict and the WHO/FAO equations. TDEE estimates assume the activity factor matches reality; activity self-reporting overshoots by 30-50% in most NHANES respondents, which is why beginners should start one tier below their gut estimate.

The Formula

Variables

• W — Body weight in kilograms
• H — Height in centimeters
• A — Age in years
• BMR — Basal metabolic rate (kcal/day)
• Activity factor — 1.2 sedentary, 1.375 light, 1.55 moderate, 1.725 very active, 1.9 extra active
• TDEE — Total daily energy expenditure (kcal/day)

Worked Example

Aisha, 35, 165 cm, 68 kg, lightly active office worker who walks 30 min after dinner. Step 1: BMR = (10 * 68) + (6.25 * 165) - (5 * 35) - 161 = 680 + 1031.25 - 175 - 161 = 1,375 kcal/day. Step 2: TDEE = 1,375 * 1.375 = 1,891 kcal/day. Step 3: For a half-kilo per week fat loss, target a 500 kcal/day deficit: 1,891 - 500 = 1,391 kcal/day intake. Step 4: After 4 weeks at 1,391 kcal Aisha lost 1.6 kg, slower than the projected 2 kg. Adjusted TDEE = (intake + lost weight x 7700 kcal/kg / days) = (1,391 + (1.6 * 7700)/28) = 1,391 + 440 = 1,831, suggesting her real activity factor is closer to 1.33 than 1.375. She drops intake to 1,330 kcal/day to maintain the half-kilo per week pace.

Methodology

TDEE prediction starts with BMR estimated from anthropometric variables. The Mifflin-St Jeor equation (1990) was derived from indirect calorimetry of 498 subjects and validated by the Academy of Nutrition and Dietetics (then the American Dietetic Association) in 2005 as the most accurate predictive equation for both healthy and obese adults, predicting measured RMR within 10% in 80% of cases. The Harris-Benedict equation (1919, revised 1984) overestimates RMR by 5-15% in modern populations because the original sample had different body compositions. The Katch-McArdle equation (1996) uses lean body mass instead of total weight, giving better accuracy in athletic and very lean populations. The activity factors (1.2 to 1.9) come from PAL (physical activity level) data compiled by FAO/WHO/UNU in 2001 from doubly-labeled water studies, which trace deuterium and oxygen-18 to measure actual CO2 production over 1-2 weeks. The thermic effect of food represents 8-12% of intake on mixed diets and is folded into the activity multiplier. TDEE values are point estimates with population standard deviations of 200-400 kcal/day; individuals can fall 500 kcal in either direction from the predicted value due to NEAT, gut microbiome differences, and genetic variation in mitochondrial efficiency.

When to Use This Calculator

Registered dietitians use TDEE as the starting point for medical nutrition therapy in patients with diabetes, kidney disease, or post-bariatric surgery, where caloric precision matters for metabolic control. Sports nutritionists working with endurance athletes (cyclists, runners) calculate TDEE to plan training-day vs. recovery-day intake; Tour de France riders can hit TDEE values of 8,000-9,000 kcal/day during mountain stages. Bodybuilders use TDEE to plan recomposition phases with a 200-500 kcal surplus during bulks and 300-500 kcal deficit during cuts. Government nutrition agencies including the USDA use TDEE distributions to set Recommended Dietary Allowances and design school lunch caloric targets. Doctors managing patients with eating disorders use TDEE to identify dangerously low intake that requires intervention.

Common Mistakes to Avoid

Selecting an activity factor one tier too high inflates TDEE by 175-250 kcal at typical body weights; this is why beginners often plateau on what they think is a deficit. Treating TDEE as fixed across a weight loss phase ignores adaptive thermogenesis and shrinking body mass; recalculate every 4-5 kg of change. Eating back exercise calories on top of an activity factor that already includes them double-counts and erases the deficit. Using the Harris-Benedict equation instead of Mifflin-St Jeor overshoots BMR by 60-200 kcal in modern populations. Trusting fitness tracker calorie burns from heart rate alone produces 30-60% errors, especially for resistance training and walking, per a 2017 Stanford study (Shcherbina et al., J Pers Med).

Practical Tips

• One pound of body fat stores 3,500 kcal; one kilogram stores about 7,700 kcal. A 500 kcal/day deficit projects to 1 lb (0.45 kg) per week, but real losses run 70-85% of theoretical because BMR adapts downward 5-15% during sustained restriction (Rosenbaum et al., NEJM 1995).
• Beginners should pick the activity factor one tier below their gut estimate. A 2008 doubly-labeled water study found self-reported very active subjects had real activity factors averaging 1.55-1.65, not 1.725-1.9.
• Don't drop below 22 kcal/kg lean body mass per day. For a 60 kg woman with 25% body fat (45 kg LBM), that's a floor of about 990 kcal. Going under this for more than 2-3 weeks triggers metabolic adaptation, lean mass loss, and amenorrhea risk.
• Recalculate TDEE every 4-5 kg of weight change. A 70 kg person who loses 5 kg drops their TDEE by about 100 kcal/day from BMR alone (10 kcal per kg from the Mifflin equation), plus another 50-100 kcal from reduced activity cost.
• Don't double-count exercise calories if you used activity factor 1.55 or higher. The factor already includes structured workouts. Add extra calories only if you sit at 1.2 (sedentary) and want to credit specific bouts.
• NEAT (non-exercise activity thermogenesis) accounts for 200-900 kcal/day in identical-twin studies and explains most individual variance in weight regulation (Levine et al., Mayo Clinic). Standing instead of sitting burns roughly 50 kcal/hour extra; walking 7,500 steps adds 250-400 kcal over a sedentary baseline.

Last updated: May 04, 2026 · Last reviewed: May 2026 — NutritionCalcs Editorial Team · About our methodology