Estimate adult Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE) using Mifflin-St Jeor or Katch-McArdle, with optional custom calorie adjustments and Atwater macronutrient breakdowns.
| Activity Tier | Multiplier | Est. Daily Maintenance |
|---|---|---|
| Sedentary | 1.2× | 2,085 kcal |
| Lightly Active | 1.375× | 2,389 kcal |
| Moderately Active | 1.55× | 2,693 kcal |
| Very Active | 1.725× | 2,997 kcal |
| Extra Active | 1.9× | 3,301 kcal |
Total Daily Energy Expenditure (TDEE) estimates the total calories an adult burns in 24 hours by multiplying Basal Metabolic Rate (BMR) by a physical activity factor (1.2 to 1.9). The default Mifflin-St Jeor (1990) equation computes BMR = 10 × Weight(kg) + 6.25 × Height(cm) − 5 × Age(y) + s (where s = +5 for males and −161 for females).
US Imperial inputs (feet/inches and pounds) are first normalized to exact metric units (1 inch = 2.54 cm, 1 lb = 0.45359237 kg). When body fat percentage is unknown, BMR is estimated via Mifflin-St Jeor (1990); when body fat percentage is known, users can select Katch-McArdle: BMR = 370 + 21.6 × LeanBodyMass(kg). Maintenance TDEE equals BMR × ActivityMultiplier. Macronutrient grams are derived using USDA Atwater general energy factors: 4 kcal/g for protein, 4 kcal/g for carbohydrate, and 9 kcal/g for dietary fat.
Using Mifflin-St Jeor (1990): BMR = 10(80) + 6.25(180) − 5(30) + 5 = 800 + 1,125 − 150 + 5 = 1,780 kcal/day.
BMR: 1,780 kcal/day | Maintenance TDEE (1.55×): 2,759 kcal/day | Balanced Macros (30/40/30): 207g Protein, 276g Carbs, 92g Fat.
Using Mifflin-St Jeor (1990): BMR = 10(62) + 6.25(165) − 5(28) − 161 = 620 + 1,031.25 − 140 − 161 = 1,350 kcal/day.
BMR: 1,350 kcal/day | Maintenance TDEE (1.375×): 1,857 kcal/day | Balanced Macros (30/40/30): 139g Protein, 186g Carbs, 62g Fat.
Basal Metabolic Rate (BMR) is the energy your body expends at complete rest to maintain vital physiological functions (breathing, circulation, cellular repair). Total Daily Energy Expenditure (TDEE) adds physical activity, movement, and the thermic effect of food to BMR by multiplying BMR by an activity factor (1.2 to 1.9), representing your estimated daily maintenance calories.
For most adults who do not know their exact body fat percentage, the Mifflin-St Jeor (1990) equation is the most widely validated predictive equation in clinical nutrition reviews. If you have a reliable estimate of your body fat percentage (especially for leaner or more muscular individuals), Katch-McArdle can provide a closer estimate because it calculates BMR directly from Lean Body Mass (LBM).
The traditional 3,500 kcal per pound rule assumes energy expenditure stays completely static as body weight changes. In reality, as body mass decreases, both resting metabolic rate and the energy cost of movement decrease (metabolic adaptation). Therefore, daily calorie adjustments should be treated as initial planning estimates and adjusted periodically based on real-world trends.
PeekAndDo uses the standard USDA Atwater general energy factors: Protein provides 4 kcal per gram, Carbohydrates provide 4 kcal per gram, and Dietary Fat provides 9 kcal per gram. For example, on a 2,400 kcal target with a 30% Protein / 40% Carbs / 30% Fat split, protein is (2,400 × 0.30) / 4 = 180g, carbs are (2,400 × 0.40) / 4 = 240g, and fat is (2,400 × 0.30) / 9 = 80g.
No. Commonly cited values like 1,200 kcal/day for women and 1,500 kcal/day for men are general population screening heuristics rather than universal clinical thresholds. Individual nutritional requirements vary widely with stature, lean body mass, and activity. Aggressive daily deficits (>750 kcal/day) or intakes below 1,200 kcal/day should be reviewed with a registered dietitian or physician.