Calorie, BMR, and TDEE Basics
How basal metabolic rate and total daily energy expenditure differ, how to set a calorie deficit or surplus, and numeric examples.
8 min read · Last updated: July 13, 2026
Calories as energy units
A dietary calorie (kcal) is the energy needed to raise 1 kg of water by 1°C — in practice, the unit on food labels. Your body burns calories at rest, during movement, and digesting food. Weight change follows energy balance: sustained calorie intake above expenditure leads to gain; below leads to loss. One pound of body fat stores roughly 3,500 kcal, so a daily deficit of 500 kcal targets about 1 lb per week — a common planning shortcut, though individual results vary. Water weight, sodium, and glycogen can shift scale weight day to day independent of fat change.
Basal metabolic rate (BMR)
BMR is the energy your body needs at complete rest — breathing, circulation, cell repair — before deliberate activity. It depends on age, sex, height, and weight. The Mifflin-St Jeor equation (widely used): 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 woman, 65 kg, 165 cm → BMR ≈ 10×65 + 6.25×165 − 5×30 − 161 ≈ 1,386 kcal/day at rest. A 35-year-old man at 82 kg and 178 cm → BMR ≈ 10×82 + 6.25×178 − 5×35 + 5 ≈ 1,778 kcal/day. BMR is the floor estimate, not a recommended diet level.
Total daily energy expenditure (TDEE)
TDEE = BMR × activity multiplier — your full daily burn including work, exercise, and daily movement. Common multipliers: sedentary (desk job, little exercise) 1.2; lightly active (1–3 days/week) 1.375; moderately active (3–5 days) 1.55; very active (6–7 days) 1.725; extra active (physical job + training) 1.9. The same woman with BMR 1,386 and a moderate activity level: TDEE ≈ 1,386 × 1.55 ≈ 2,148 kcal/day. That is her maintenance intake estimate. The man above at 1.55 multiplier: TDEE ≈ 2,756 kcal/day. Pick the multiplier that matches an average week, not your most active day.
Setting a deficit or surplus
Fat loss: eat below TDEE. A 500 kcal/day deficit on 2,148 TDEE → ~1,648 kcal target. Muscle gain: eat above TDEE with adequate protein — often +200 to 300 kcal above maintenance. Aggressive deficits below BMR are rarely sustainable and can cost lean mass. Revisit TDEE every 4–6 weeks as weight changes — a lighter body burns fewer calories, so targets should adjust. If scale weight stalls for 2–3 weeks at consistent intake, reduce by 100–150 kcal or add modest activity rather than slashing calories in half.
Macros and water — supporting inputs
Protein supports muscle during a deficit — many adults aim for 1.6–2.2 g per kg body weight. At 65 kg that is 104–143 g protein daily (416–572 kcal from protein). Carbohydrates and fats fill remaining calories based on preference and training load. Endurance athletes often skew higher carb; low-carb approaches shift toward fat. Water needs scale with body size and activity; a common baseline is ~30–35 ml per kg body weight daily, plus extra for exercise and climate. At 65 kg, that is roughly 2–2.3 liters before workouts. These refine a calorie target but do not replace the TDEE starting point.
Tracking progress without overfitting
Weigh yourself under consistent conditions (morning, after bathroom) and use a 7–14 day average. Compare average weight trend to intake every few weeks. If you eat at calculated maintenance and weight is stable, your TDEE estimate is validated. If you lose faster than planned, add calories; if slower, verify portion accuracy before cutting further. Wearables estimate burn but can be off by 10–30%; food labels and kitchen scales matter more for intake. BMR and TDEE equations are starting estimates — your logged trend is the feedback loop.
Calculate yours on CalcVo
Start with the CalcVo BMR Calculator for resting burn, then the TDEE Calculator for maintenance calories with activity level. The Calorie Calculator sets deficit or surplus targets. Use the Macro Calculator to split protein, carbs, and fat, the Water Intake Calculator for hydration, and the Ideal Weight Calculator for context on long-term goals. All estimates run locally — adjust based on real-world progress over several weeks, not a single day's scale reading.