Calculate your daily calorie needs based on the Mifflin-St Jeor equation, recommended by the Academy of Nutrition and Dietetics.
BMR = 10×W + 6.25×H - 5×A + sJust snap a photo of your food — CalZen recognizes it instantly and tracks your calories, macros, water, and more.
This calculator uses the Mifflin-St Jeor equation (1990) to estimate your Basal Metabolic Rate (BMR) — the number of calories your body needs at complete rest. It then multiplies your BMR by an activity factor to determine your Total Daily Energy Expenditure (TDEE).
The Mifflin-St Jeor equation was found to be the most accurate predictive equation for healthy individuals in a systematic review of 18 studies by Frankenfield et al., published in the Journal of the American Dietetic Association (2005). It predicts resting metabolic rate within 10% of measured values in more subjects than any other equation.
| Formula | Equation | Accuracy |
|---|---|---|
| Mifflin-St Jeor (default) | 10×W + 6.25×H - 5×A ± s | Most accurate (ADA) |
| Harris-Benedict (revised) | 13.4×W + 4.8×H - 5.7×A + 88.4 (M) | Tends to overestimate |
| Katch-McArdle | 370 + 21.6×LBM | Best for athletes (needs body fat %) |
The USDA Dietary Guidelines for Americans (2020-2025) provide estimated calorie needs by age, sex, and activity level:
| Age | Women (sed./mod./active) | Men (sed./mod./active) |
|---|---|---|
| 19-25 | 2,000 / 2,200 / 2,400 | 2,400-2,600 / 2,800 / 3,000 |
| 26-30 | 1,800 / 2,000 / 2,400 | 2,400 / 2,600 / 3,000 |
| 31-50 | 1,800 / 2,000 / 2,200 | 2,200 / 2,400 / 2,800 |
| 51-60 | 1,600 / 1,800 / 2,200 | 2,200 / 2,400 / 2,600 |
| 61+ | 1,600 / 1,800 / 2,000 | 2,000 / 2,200 / 2,600 |
For safe weight loss, the CDC recommends losing 1-2 pounds (0.5-1 kg) per week through a calorie deficit of 500-1,000 kcal/day. Minimum safe intake: 1,200 kcal/day for women, 1,500 kcal/day for men (NHLBI).
Research consistently shows that people who track what they eat are significantly more successful at losing weight:
| Study | Finding | Source |
|---|---|---|
| Kaiser Permanente (2008) | People who kept daily food records lost 2× more weight | Am J Prev Med |
| Harvey et al. (2019) | Only 15 min/day of food logging needed for results | Obesity |
| Berry et al. (2021) | Digital self-monitoring = -2.87 kg significant weight loss | Obesity Reviews |
| Huntriss et al. (2024) | 50% of active users achieved 5%+ weight loss | Obesity Sci & Pract |
| AI-Assisted Tracking (2024) | 64% maintain changes vs 23% manual tracking | JMIR |
"Those who kept daily food records lost twice as much weight as those who kept no records."
— Jack Hollis, Ph.D., Kaiser Permanente
It depends on your age, sex, height, weight, and activity level. Most adults need between 1,600-3,000 calories per day. Use the calculator above for a personalized estimate based on the Mifflin-St Jeor equation.
The Mifflin-St Jeor equation (1990) is considered the most accurate by the Academy of Nutrition and Dietetics. A 2005 systematic review by Frankenfield et al. found it predicts resting metabolic rate within 10% of measured values in more subjects than any other formula.
BMR (Basal Metabolic Rate) is the calories your body burns at complete rest — just to keep you alive. TDEE (Total Daily Energy Expenditure) is your BMR multiplied by your activity level. TDEE is the number you should use to plan your diet.
The CDC recommends a deficit of 500-1,000 calories per day for safe weight loss of 0.5-1 kg (1-2 lbs) per week. Never go below 1,200 kcal/day (women) or 1,500 kcal/day (men) without medical supervision.
The Mifflin-St Jeor equation predicts BMR within ±10% for most healthy adults. However, individual variation exists. Use the calculator as a starting point and adjust based on your actual results over 2-3 weeks.
Both matter. Total calories determine whether you gain, lose, or maintain weight. Macros (protein, carbs, fat) determine your body composition, energy, and health. For best results, track both — an app like CalZen makes this easy with AI food recognition.
According to NHLBI guidelines: 1,200 kcal/day for women and 1,500 kcal/day for men. Very low calorie diets (below 800 kcal/day) should only be followed under medical supervision.
Yes. A landmark Kaiser Permanente study (2008) found that people who kept daily food records lost twice as much weight. A 2024 study in JMIR showed that AI-assisted tracking helps 64% of users maintain dietary changes long-term, vs only 23% with manual methods.
1. Mifflin MD, St Jeor ST, et al. Am J Clin Nutr. 1990;51(2):241-7. DOI
2. Roza AM, Shizgal HM. Am J Clin Nutr. 1984;40(1):168-182. DOI
3. Frankenfield D, et al. J Am Diet Assoc. 2005;105(5):775-789. DOI
4. USDA. Dietary Guidelines for Americans 2020-2025. Link
5. Harvey J, et al. Obesity. 2019;27(3):380-384. PMC
6. CDC. Losing Weight. Link
7. NHS. Understanding Calories. Link