For informational purposes only. Not a substitute for professional medical advice. Consult a healthcare provider before making health decisions.
Daily Calories Calculator — TDEE, BMR & Mifflin-St Jeor Online
Enter your sex, age, height, weight, activity level, and goal (maintain, lose, gain) and the page returns your estimated daily calorie target with a default macro breakdown (protein/carbs/fat). The Basal Metabolic Rate (BMR) uses the Mifflin-St Jeor equation, which since the 1990s has been the most accurate of the popular BMR formulas for sedentary-to-moderately-active populations (Harris-Benedict 1919 systematically over-estimates by 5%; Katch-McArdle requires lean body mass which most people don't know precisely). The activity multiplier scales BMR to TDEE (Total Daily Energy Expenditure). Goal modifies TDEE by ±500 kcal/day for moderate loss/gain, ±250 for slow change.
About calorie calculation
Mifflin-St Jeor BMR (1990): 10 × weight(kg) + 6.25 × height(cm) − 5 × age(yr) + 5 (men) or − 161 (women). Activity multipliers: sedentary 1.2 (desk job, no exercise), light 1.375 (light exercise 1-3 days/wk), moderate 1.55 (moderate exercise 3-5 days/wk), very active 1.725 (intense 6-7 days/wk), extra 1.9 (very intense daily training + physical job). The −500 kcal/day deficit for ~0.5 kg/week loss comes from the long-standing 7,700 kcal-per-kg-of-body-fat heuristic — useful as a planning rule even though metabolic adaptation makes the actual loss tail off over months. Critical caveat: this is an educational estimator, not medical or nutritional advice. Real metabolic rates vary by ±15% individual to individual at the same demographics, leptin/ghrelin signaling shifts during prolonged deficits, and people with metabolic conditions, pregnancy, or eating disorders should work with a qualified dietitian or doctor rather than a web calculator. The macro split here is a starting default (e.g. 30/40/30 for general fitness, 40/30/30 for cutting, 25/55/20 for endurance) — actual macro needs depend on training type and individual response.
- Mifflin-St Jeor BMR equation (most accurate for sedentary-to-moderate)
- 5-step activity multiplier (sedentary 1.2 → extra 1.9)
- Goal adjustment ±500 kcal for moderate loss/gain
- Default macro split per goal (general fitness / cutting / endurance)
- Editable height, weight, age, sex inputs
- Reactive — recalcs as you tune any input
- All math runs locally in your browser — no upload
- Includes the 7,700 kcal-per-kg fat-loss planning heuristic explained
- Educational tool — explicit disclaimer about medical advice
- Useful for general fitness planning, gym macro targets, intuitive eating baseline
Free. No signup. Your inputs stay in your browser. Ads via Google AdSense (consent required).
Frequently asked questions
Which BMR formula is most accurate — Mifflin-St Jeor or Harris-Benedict?
Mifflin-St Jeor (1990) is more accurate by ~5% across most modern populations. Harris-Benedict (1919) systematically over-estimates because it was derived from early-20th-century cohorts that ate differently and were typically more sedentary. Katch-McArdle is theoretically more accurate (uses lean body mass directly rather than total weight) but most people don't know their precise LBM without DEXA or hydrostatic weighing. For practical use without lab data, Mifflin-St Jeor is the default in clinical nutrition software and the calculator above.
Why does my actual weight loss differ from the prediction?
The 7,700 kcal/kg planning rule (Wishnofsky 1958) is a static heuristic, but Hall et al. 2011 (Lancet 378:826-837) showed real weight-loss dynamics are non-linear. Adaptive thermogenesis reduces TDEE 5-15% during prolonged deficits (Müller & Bosy-Westphal 2013), NEAT down-regulates by 100-300 kcal/day, and BMR drops mechanically as bodyweight drops. Practical implication: actual 12-week weight loss tends to run ~75-85% of the linear prediction (per Hall 2011). Adjust intake monthly based on actual weight trend rather than the initial calculation.
Can I just go below the 1200/1500 cal/day floor?
Risky territory. The 1200 cal/day floor for women and 1500 for men comes from clinical practice (ACSM, Academy of Nutrition and Dietetics) reflecting minimum intake to meet micronutrient RDIs across the broad population. Below this, deficiencies of iron, calcium, B-vitamins, and essential fatty acids accumulate. People with eating disorder history, pregnancy, breastfeeding, or chronic medical conditions should not use this calculator unsupervised — consult a registered dietitian or physician for medically-supervised low-calorie protocols (e.g., VLCDs).
How often should I recalculate as I lose weight?
Monthly recalculation is standard practice. As you lose weight your BMR drops mechanically — every kg of fat-free mass burns ~22 kcal/day, every kg of fat ~3.6 kcal/day per the Hall 2011 model — so the same caloric intake represents a smaller deficit relative to your now-lower TDEE. If your weight stalls for 2-3 weeks despite hitting your intake target, recalculate using your current weight and adjust intake by 100-200 kcal/day. Don't recalculate weekly; week-to-week weight fluctuates ±1-2 kg from water/glycogen alone.
What's the difference between BMR and TDEE?
BMR (Basal Metabolic Rate) is the energy your body burns at complete rest just to maintain vital functions — heart pumping, lungs breathing, neurons firing, kidneys filtering. TDEE (Total Daily Energy Expenditure) adds the activity multiplier on top: NEAT (non-exercise activity thermogenesis), exercise, and the thermic effect of food (~10% of intake). The calculator uses Mifflin-St Jeor for BMR then multiplies by the activity coefficient (1.2 sedentary → 1.9 extra-active) to get TDEE. Daily calorie targets for maintain/lose/gain are based on TDEE, not BMR.
Sources (6)
- Mifflin, M. D., St Jeor, S. T., Hill, L. A., Scott, B. J., Daugherty, S. A., & Koh, Y. O. (1990). A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition, 51(2), 241–247 — most accurate BMR formula for sedentary-to-moderately-active populations (~5% better than Harris-Benedict).
- Harris, J. A., & Benedict, F. G. (1919). A Biometric Study of Basal Metabolism in Man. Carnegie Institution of Washington, Publication No. 279 — original BMR equations; systematically over-estimates by ~5% relative to modern populations.
- Wishnofsky, M. (1958). Caloric equivalents of gained or lost weight. American Journal of Clinical Nutrition, 6(5), 542–546 — origin of the 3,500 kcal/lb (≈ 7,700 kcal/kg) heuristic for body-fat energy equivalent (derived from Bozenrad's adipose-tissue chemistry).
- Hall, K. D., Sacks, G., Chandramohan, D., Chow, C. C., Wang, Y. C., Gortmaker, S. L., & Swinburn, B. A. (2011). Quantification of the effect of energy imbalance on bodyweight. The Lancet, 378(9793), 826–837 (27 August 2011) — quantitative model of metabolic adaptation; weight response half-time ≈ 1 year; greater adiposity → larger steady-state loss.
- Institute of Medicine (US) Panel on Macronutrients (2005). Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids — Acceptable Macronutrient Distribution Ranges (AMDR). National Academies Press, Washington DC — Protein 10–35%, Carbs 45–65%, Fat 20–35% of daily energy.
- Donnelly, J. E., Blair, S. N., Jakicic, J. M., Manore, M. M., Rankin, J. W., & Smith, B. K. (2009). American College of Sports Medicine Position Stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Medicine & Science in Sports & Exercise, 41(2), 459–471 — clinical-practice basis for the 1200 kcal/day (women) and 1500 kcal/day (men) lower-bound floors in supervised weight-loss interventions.
These are the original publications the formulas in this tool are based on. Locate them by journal name and year on Google Scholar or PubMed.
By Marco B. ·