PonyatnoHow it's calculated
Basal metabolic rate (energy used at complete rest) is calculated with the Mifflin-St Jeor equation (1990): 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) + 5 for men and … − 161 for women.
Maintenance = BMR × activity factor: 1.2 sedentary, 1.375 light, 1.55 moderate, 1.725 very active, 1.9 extremely active.
Gentle weight loss is maintenance minus 15%, weight gain is maintenance plus 10%. The weight-loss figure never goes below 1200 kcal for women or 1500 kcal for men.
Protein is 0.8–1.6 g per kilogram of body weight. Fat is 25–35% of maintenance calories, shown in grams (1 g of fat = 9 kcal).
What to know
What the numbers mean
Mifflin-St Jeor is one of the most accurate equations for healthy adults, but it is still an estimate: a real person's needs can differ by about ±10%. Treat the result as a starting point and watch how your weight changes over 2–3 weeks.
The lower protein figure (0.8 g/kg) is the WHO minimum requirement for adults; the upper one (1.6 g/kg) is more relevant with regular strength training and in older age.
When this estimate doesn't apply
Pregnancy and breastfeeding: needs are different and are best discussed with your doctor. Under 18. Eating disorders — counting calories can do harm here; a specialist will help more than a calculator. Kidney disease: the upper protein figure may be too high. With a lot of muscle or severe obesity, the equation is less accurate.
Weight loss and blood tests
If your weight won't budge, or drops very fast, calories aren't always the explanation. Glucose and HbA1c, a lipid panel, TSH and ferritin show what is happening with your metabolism, thyroid and iron stores. It's worth having them done before a big change in eating and going over the results with a doctor.
This calculator is a reference tool, not a diagnosis. Laboratory ranges differ, and the result depends on your health, medicines and other tests. Discuss it with your doctor.
FAQ
How many calories should I eat to lose weight?
The calculator shows a gentle option — 15% below maintenance. Very large deficits are harder to stick to and more often end in rebound eating.
What is BMR?
Basal metabolic rate is the energy your body uses at complete rest — for breathing, heart and brain function and keeping warm. Eating below it for long periods is not recommended.
Why isn't my weight changing when I eat the calculated amount?
The equation can be off by ±10%, activity is often overestimated and food underestimated. So the result is only a starting point. If your weight stays put on clearly modest intake, ask your doctor about checking TSH and other tests.
How do I choose my activity level?
Count only deliberate exercise and time on your feet at work. An office job plus two workouts a week is "light", not "moderate". If in doubt, pick the lower level.
Can I use this calculator during pregnancy?
No. During pregnancy and breastfeeding, energy and protein needs are different and change over time — discuss them with your doctor or midwife.
Sources
Formulas and cut-offs follow clinical guidelines — see sources below.
- Mifflin MD et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241–247.
- WHO/FAO/UNU. Protein and amino acid requirements in human nutrition. WHO Technical Report Series 935; 2007.