BMR Calculator — How Many Calories Should I Eat Per Day

Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest to sustain essential functions: heartbeat, breathing, brain activity, temperature regulation and cell renewal. According to the WHO, BMR accounts for 60–75% of total daily energy expenditure. Understanding your BMR gives you the lower boundary of safe calorie intake — going below it consistently is dangerous even when trying to lose weight. Key drivers of BMR: body weight, height, age, sex and body composition. People with more muscle mass have a higher BMR because muscle tissue is metabolically more active than fat.

The Mifflin-St Jeor equation (1990) is currently the most accurate BMR formula for people with typical modern lifestyles. It predicts within 10% of measured BMR in the majority of cases. Men: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5. Women: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161. The difference in constants (+5 for men vs −161 for women) reflects natural differences in hormonal profile and body composition. The American Dietetic Association (ADA) recommends this formula as the primary equation for clinical practice.

The original Harris-Benedict equation (1919) was the first scientifically validated BMR model. It was revised and improved in 1984. Men: BMR = 88.362 + (13.397 × weight kg) + (4.799 × height cm) − (5.677 × age). Women: BMR = 447.593 + (9.247 × weight kg) + (3.098 × height cm) − (4.330 × age). Harris-Benedict slightly overestimates BMR for sedentary individuals (+5% on average) and is less accurate for people with obesity. It may produce more relevant results for athletes or people with unusually high lean body mass.

TDEE (Total Daily Energy Expenditure) is the full picture of your daily calorie burn, accounting for physical activity. Formula: TDEE = BMR × activity multiplier. Multipliers: 1.2 — sedentary (desk job, no exercise); 1.375 — lightly active (1–3 workouts/week); 1.55 — moderately active (3–5 workouts/week); 1.725 — very active (6–7 workouts/week); 1.9 — extra active (physical labour or twice-daily training). TDEE = the number of calories to maintain your current weight. To lose weight, eat below TDEE. To gain muscle, eat above TDEE.

A safe calorie deficit for weight loss is 15–20% below TDEE, resulting in 0.3–0.7 kg (0.6–1.5 lb) of weight loss per week. A 20% deficit means roughly −500 kcal/day, which gives approximately 0.5 kg/week. A smaller deficit (10–15%) produces slower but more sustainable results with minimal muscle loss and no metabolic slowdown. A larger deficit (>25%) speeds up weight loss only for the first 2–4 weeks — after that the body adapts via adaptive thermogenesis, reducing BMR by 10–25%. Minimum safe intake: 1200 kcal/day for women, 1500 kcal/day for men — regardless of calculated BMR.

Macronutrients (protein, fat, carbohydrates) provide all dietary energy. Standard balanced split for moderate activity: protein 25–30%, fat 25–30%, carbs 40–50%. For weight loss: increase protein to 30–35% (1.8–2.4 g per kg of body weight) to preserve muscle mass and improve satiety. For muscle gain: increase carbs to 50–55% to fuel training. Fat should not drop below 0.8 g/kg — essential for hormonal health. Calorie values: protein 4 kcal/g, carbs 4 kcal/g, fat 9 kcal/g. Our calculator computes macro targets automatically based on your selected goal.

Metabolism slows due to: ageing (approximately 2–3% per decade after 30 from natural muscle loss), prolonged very-low-calorie diets (adaptive thermogenesis), poor sleep (fewer than 7 hours raises cortisol and reduces BMR by 5–20%), sedentary lifestyle, and hypothyroidism. Proven ways to raise metabolic rate: strength training to build muscle (most effective long-term strategy), adequate protein intake (thermic effect of protein is 20–30% vs 5–10% for carbs), regular meal timing, 7–9 hours of quality sleep, and sufficient hydration (even 2% dehydration measurably reduces metabolic rate).

Depends on age, height, weight and activity level. Approximate TDEE ranges for women: sedentary — 1500–1800 kcal; moderately active — 1800–2200 kcal; very active — 2200–2600 kcal. For weight loss, subtract 15–20% from these figures. For precise numbers, use the calculator above — it accounts for your individual parameters.

Approximate TDEE for men: sedentary — 2000–2400 kcal; moderately active — 2400–2800 kcal; very active — 2800–3500 kcal. Men generally have higher BMR due to greater lean muscle mass. Use the calculator for your exact figure.

BMR is the calories your body burns at complete rest — think lying still all day, not digesting food. TDEE is your real-world daily burn: BMR plus all activity (movement, exercise, digestion, fidgeting). For most people TDEE = BMR × 1.4–1.6. For weight management, always work from TDEE, not BMR.

Not recommended as a regular pattern. BMR represents the minimum calories for organ function. Eating consistently below BMR causes the body to slow metabolism, break down muscle tissue and downregulate hormones (leptin, thyroid). This makes future weight loss harder. Absolute minimum safe intake: 1200 kcal for women, 1500 kcal for men — regardless of BMR.

Losing 1 kg of fat requires a deficit of approximately 7700 kcal. To lose 1 kg/week you need a daily deficit of 1100 kcal — which is aggressive and unsustainable for most people. Optimal pace: 0.3–0.7 kg/week (deficit 300–700 kcal/day). Best approach: combine dietary reduction with exercise — for example, −400 kcal from food and −300 kcal burned in training.

This is adaptive thermogenesis — the body's protective response to calorie restriction. After several weeks of a large deficit, BMR drops by 10–25%, spontaneous activity (NEAT) decreases and hormones like leptin and thyroid hormones fall. This is why diets often "stop working" after 4–8 weeks. Solutions: diet breaks or refeed days, preserving muscle through strength training, moderate deficit no greater than 20%.

General recommendation: 1.6–2.4 g of protein per kg of body weight for active individuals, with the higher end (2.0–2.4 g/kg) during a calorie deficit to preserve muscle. Protein has the highest thermic effect of any macronutrient — 20–30% of protein calories are burned during digestion itself, which also contributes to a higher effective deficit. Our calculator estimates your daily protein target based on your goal.

BMR decreases approximately 2–3% per decade after age 30, mainly because of gradual muscle loss (sarcopenia). A 50-year-old has roughly 4–6% lower BMR than a 30-year-old at the same weight. The good news: regular strength training largely offsets this decline by maintaining or building muscle mass, keeping metabolism elevated regardless of age.