Daily Calorie Needs Calculator
Use this Daily Calorie Needs Calculator to find your BMR and TDEE, see your calorie targets for weight loss, maintenance, and muscle gain, compare three BMR formulas side by side, and get a full macro breakdown with weight-change timeline projections.
The Three BMR Formulas Explained
Basal Metabolic Rate is calculated differently across several validated formulas. Each was derived from a different study population and has specific strengths. This calculator uses Mifflin-St Jeor as the primary result, but shows all three for comparison.
Mifflin-St Jeor (Recommended)
Published in 1990 and validated across a large, diverse population, this is considered the most accurate BMR formula for most adults by the Academy of Nutrition and Dietetics. For men: BMR = 10W + 6.25H - 5A + 5. For women: BMR = 10W + 6.25H - 5A - 161, where W is weight in kg, H is height in cm, and A is age in years.
Harris-Benedict (Revised 1984)
The original Harris-Benedict equation from 1919 was revised by Roza and Shizgal in 1984. It is still widely used in clinical settings but tends to slightly overestimate BMR, particularly in older adults and those with higher body fat. For men: 88.36 + 13.4W + 4.8H - 5.68A. For women: 447.6 + 9.25W + 3.10H - 4.33A.
Schofield
The Schofield equations use age-banded coefficients rather than a single formula, which makes them more accurate for extreme age ranges (under 18 or over 60). They are used by the UK Scientific Advisory Committee on Nutrition and the World Health Organization in clinical contexts. Values vary by age band and sex.
BMR Formula Results at Common Body Profiles
| Profile | Mifflin | Harris-B | Schofield |
|---|---|---|---|
| Woman, 30, 163 cm, 65 kg | 1,416 kcal | 1,458 kcal | 1,435 kcal |
| Man, 30, 175 cm, 80 kg | 1,855 kcal | 1,918 kcal | 1,871 kcal |
| Woman, 55, 163 cm, 70 kg | 1,341 kcal | 1,383 kcal | 1,298 kcal |
| Man, 55, 175 cm, 85 kg | 1,855 kcal | 1,918 kcal | 1,847 kcal |
Understanding Your Calorie Numbers
Why TDEE Matters More Than BMR
BMR is what you burn at complete rest. TDEE is what you actually burn in a day. The gap between the two is entirely driven by movement, and that gap is larger than most people expect. A sedentary person burns about 20% more than their BMR. A very active person burns nearly double their BMR daily.
The 3,500 Calorie Rule
The longstanding rule that a 3,500 kcal deficit equals 1 lb (0.45 kg) of fat loss is a useful rough guide, though research shows the relationship is not perfectly linear as body composition changes over time. A 400 kcal/day deficit produces approximately 0.35 kg per week in the short term — a sustainable, evidence-supported rate of loss that preserves more muscle than aggressive restriction.
Why Not Go Lower?
Very low calorie diets (under 1,200 kcal for women or 1,500 kcal for men) increase muscle loss, reduce metabolic rate, elevate cortisol, and are associated with higher rates of weight regain. A moderate deficit sustained over months produces better long-term outcomes than aggressive restriction followed by rebound eating.
Frequently Asked Questions
How many calories do I need per day to lose weight?
You need to consume fewer calories than your TDEE. A deficit of 300 to 500 kcal/day is widely recommended as the sustainable range, producing roughly 0.25 to 0.5 kg per week of fat loss. This calculator uses a 400 kcal deficit as the default. More aggressive deficits (500 to 750 kcal) can be used short-term but increase the risk of muscle loss and metabolic adaptation.
Why do I seem to need fewer calories than the calculator suggests?
BMR formulas predict average values. Individual metabolic rate can be 10 to 20% lower than the formula predicts, particularly in people who have previously lost significant weight, those with hypothyroidism, or those with lower muscle mass. If your real-world results suggest a lower maintenance level, trust the data: track your intake and weight over 3 to 4 weeks and adjust the calculator output accordingly.
Does eating more frequently boost metabolism?
No, not in any meaningful way. The thermic effect of food (the calories burned digesting meals) is approximately the same whether those calories are consumed in 3 meals or 6 meals per day. Total calorie intake drives energy balance, not meal frequency. Meal timing may matter for specific performance or hormonal goals, but the metabolic effect of frequency itself is negligible.
How accurate are wearable calorie trackers?
Consumer wearables typically overestimate calorie burn by 20 to 40% depending on device and activity type. Running estimates are more accurate than strength training or cycling. Heart-rate-based estimates are better than accelerometer-only devices. Use wearable data directionally (is today a higher or lower burn day than yesterday) rather than as precise caloric targets to eat back.
What is the minimum safe calorie intake?
The generally accepted minimum for adults without medical supervision is 1,200 kcal/day for women and 1,500 kcal/day for men. Going below these thresholds increases risk of nutrient deficiencies, muscle catabolism, gallstones, and hormonal disruption. Very low calorie diets (800 kcal or below) should only be used under direct medical supervision with protein supplementation and regular monitoring.
References
- Mifflin MD, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241-247. https://pubmed.ncbi.nlm.nih.gov/2305711/
- Roza AM, Shizgal HM. The Harris Benedict equation reevaluated: resting energy requirements and the body cell mass. Am J Clin Nutr. 1984;40(1):168-182. https://pubmed.ncbi.nlm.nih.gov/6741850/
- Schofield WN. Predicting basal metabolic rate, new standards and review of previous work. Hum Nutr Clin Nutr. 1985;39(Suppl 1):5-41. https://pubmed.ncbi.nlm.nih.gov/4044297/
- Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids. National Academies Press; 2005. https://www.ncbi.nlm.nih.gov/books/NBK56068/
- Hall KD, et al. Quantification of the effect of energy imbalance on bodyweight. Lancet. 2011;378(9793):826-837. https://pubmed.ncbi.nlm.nih.gov/21872751/
