Mifflin-St Jeor Formula · BMR · TDEE · Macro Breakdown
Total Daily Energy Expenditure (TDEE) represents the total number of calories your body burns in a 24-hour period. It is composed of four distinct components, each contributing a different share of your total calorie burn. Understanding these components is essential for anyone looking to manage their weight effectively, whether the goal is fat loss, muscle gain, or weight maintenance.
Basal Metabolic Rate (BMR) is the largest component, typically accounting for 60–75% of total daily energy expenditure. BMR represents the energy your body needs to maintain basic life-sustaining functions while at complete rest: breathing, blood circulation, cell production, nutrient processing, and maintaining body temperature. Even if you stayed in bed all day doing absolutely nothing, your body would still burn calories equal to your BMR. Several factors influence BMR, including body size (larger bodies burn more calories), body composition (muscle tissue burns more calories at rest than fat tissue — approximately 6–10 calories per pound per day for muscle versus 2–3 calories per pound for fat), age (BMR decreases by about 1–2% per decade after age 20, primarily due to muscle loss), sex (men generally have higher BMR due to greater muscle mass), genetics, hormonal status (thyroid function is a major regulator), and temperature (both external and internal body temperature affect metabolic rate).
Non-Exercise Activity Thermogenesis (NEAT) accounts for 15–30% of TDEE and encompasses all physical activity that is not structured exercise. This includes walking, standing, fidgeting, typing, gardening, cooking, cleaning, and even talking. NEAT varies enormously between individuals — studies have found that it can differ by as much as 2,000 calories per day between people with similar body sizes and activity levels. This variability is largely subconscious and genetically influenced. People who naturally fidget, pace, and stay on their feet burn significantly more calories through NEAT than those who are more sedentary, even if neither group exercises formally. Importantly, when people deliberately restrict calories, their bodies often subconsciously reduce NEAT — you may move less without realizing it — which partially offsets the calorie deficit and can stall weight loss.
Exercise Activity Thermogenesis (EAT) represents the calories burned through structured, intentional exercise such as running, weightlifting, swimming, cycling, or attending fitness classes. Despite receiving the most attention, EAT typically contributes only 5–15% of total daily energy expenditure for most people. This means that a one-hour workout, while beneficial for fitness and health, burns fewer calories than most people assume. For example, a 70 kg person running at a moderate pace for an hour burns roughly 500–600 calories — roughly equivalent to a large sandwich. This "exercise paradox" explains why exercise alone is often insufficient for significant weight loss without dietary changes. However, exercise provides crucial benefits beyond calorie burning: it improves cardiovascular health, builds muscle, enhances mood, improves sleep quality, and increases metabolic flexibility.
Thermic Effect of Food (TEF) accounts for approximately 10% of total daily energy expenditure. TEF represents the energy required to digest, absorb, transport, metabolize, and store the nutrients from the food you eat. Different macronutrients have different thermic effects: protein has the highest TEF at roughly 20–30% of its calories (meaning 100 calories of protein yields only 70–80 net calories after digestion), carbohydrates have a moderate TEF of 5–10%, and fats have the lowest TEF at 0–3%. This is one reason why high-protein diets are often effective for weight loss — not only does protein promote satiety and muscle preservation, but a significant portion of protein calories are "lost" to the thermic effect. Mixed meals typically have a combined TEF of about 10%, meaning that if you eat 2,500 calories per day, roughly 250 of those calories are burned through digestion and processing.
The Mifflin-St Jeor equation, published in 1990 by Mark Mifflin and Sachiko St Jeor, has become the gold standard for estimating Basal Metabolic Rate in clinical and fitness settings. It was developed by analyzing data from 498 healthy individuals, including both men and women, across a range of ages and body types. The researchers used indirect calorimetry — a technique that measures oxygen consumption and carbon dioxide production to determine energy expenditure — to establish accurate BMR measurements for each participant, then used regression analysis to derive the predictive equation.
The equation is expressed as follows: for men, BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) + 5; for women, BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) - 161. The coefficients in this equation reflect the relative contributions of each variable: weight contributes 10 calories per kilogram, height contributes 6.25 calories per centimeter (as a proxy for lean body mass), and age subtracts 5 calories per year (reflecting the age-related decline in metabolic rate). The sex-specific constants (+5 for men, -161 for women) account for the average difference in body composition between sexes — men typically have more muscle mass and less fat mass, resulting in a higher metabolic rate.
Multiple validation studies have confirmed that the Mifflin-St Jeor equation is more accurate than older equations such as the Harris-Benedict equation (1919, revised 1984) for modern populations. The Harris-Benedict equation was derived from data collected in the early 20th century and tends to overestimate BMR by 5–15% in contemporary populations, likely because modern humans are generally less active and have different body composition profiles. A 2013 systematic review published in the American Journal of Clinical Nutrition concluded that Mifflin-St Jeor provided the most accurate BMR estimates across diverse populations, making it the recommended formula for use in clinical practice and by health professionals worldwide.
Selecting the correct activity multiplier is one of the most important — and most commonly misunderstood — steps in calculating your TDEE. The activity multipliers range from 1.2 (sedentary) to 1.9 (extra active), and choosing a multiplier that is too high is a frequent cause of frustration when calorie-based diet plans don't produce expected results.
Sedentary (multiplier 1.2) applies if you have a desk job, do not exercise regularly, and spend most of your leisure time sitting or lying down. This category describes the majority of adults in modern industrialized societies. Lightly active (multiplier 1.375) describes someone who has a desk job but engages in light exercise or movement for 1–3 days per week, or someone whose job involves some standing and walking (like a teacher or retail worker) but no formal exercise. Moderately active (multiplier 1.55) applies if you exercise 3–5 days per week at a moderate intensity, or if you have a physically demanding job (construction worker, server, delivery person) combined with some exercise. Very active (multiplier 1.725) describes individuals who exercise 6–7 days per week at moderate to high intensity, or those with very physically demanding jobs. Extra active (multiplier 1.9) is reserved for elite athletes, people who exercise twice per day, or those with extremely demanding physical occupations combined with intense training.
The most common mistake is overestimating activity level. Many people who exercise 3–4 times per week but spend the remaining 23 hours of each day sitting will get more accurate results by selecting "sedentary" or "lightly active" rather than "moderately active." A good rule of thumb: estimate your exercise calories using a heart rate monitor or fitness tracker, then divide by your BMR. If your total exercise calories represent less than 15% of your BMR, you're likely sedentary. If they represent 15–30%, you're lightly active. Only if they consistently exceed 30% of your BMR should you consider yourself moderately active or higher.
For weight loss, the fundamental principle is creating a sustained calorie deficit — consuming fewer calories than your TDEE. A deficit of 500 calories per day theoretically produces a weight loss of approximately 0.45 kg (1 pound) per week, as each pound of body fat contains roughly 3,500 calories. However, this relationship is not perfectly linear in practice. As you lose weight, your BMR decreases (because a smaller body requires fewer calories to maintain), your TDEE drops, and adaptive thermogenesis — a metabolic slowdown beyond what would be predicted by weight loss alone — can further reduce your energy expenditure. This means that the same calorie deficit that produced results early in your diet may become insufficient as you get leaner, requiring periodic recalculations and adjustments.
Practical weight loss strategies include: starting with a moderate deficit of 15–20% below TDEE (which is sustainable and minimizes muscle loss); prioritizing protein intake at 1.6–2.2 grams per kilogram of body weight to preserve lean mass; incorporating resistance training to stimulate muscle retention; and using diet breaks or refeed days (temporary periods at maintenance calories) every 2–4 weeks to mitigate metabolic adaptation and improve adherence. Extremely low-calorie diets (below 1,000–1,200 calories for women or 1,400–1,600 for men) are generally discouraged without medical supervision because they accelerate muscle loss, hormonal disruption, and metabolic adaptation.
For weight gain and muscle building (often called a "lean bulk"), the approach is reversed: you need a calorie surplus of roughly 250–500 calories above TDEE. Going higher than this typically leads to excessive fat gain without proportionally more muscle. Protein should be set at 1.6–2.2 grams per kilogram of body weight per day, with remaining calories split between carbohydrates and fats based on personal preference and training demands. Carbohydrates are particularly important for individuals engaged in intense training because they fuel high-intensity exercise performance, which in turn drives the muscle-building stimulus. Aim for a weight gain rate of 0.25–0.5% of body weight per week — faster gains almost certainly include significant fat accumulation that will need to be lost later.
Underestimating portion sizes is arguably the most prevalent tracking error. Studies using doubly labeled water (the gold standard for measuring actual calorie intake) have consistently found that people underestimate their food intake by 20–50%, with overweight individuals tending to underreport more than lean individuals. This isn't usually deliberate deception — it's a genuine cognitive bias called "portion distortion." Restaurant meals are particularly problematic: a typical restaurant entree contains 1,000–1,500 calories, even when it appears to be a reasonable portion. Using a food scale (not measuring cups or visual estimates) and logging everything immediately (not at the end of the day from memory) dramatically improves tracking accuracy.
Failing to account for cooking oils, sauces, condiments, and beverages is another common pitfall. A single tablespoon of olive oil contains 120 calories — adding just two tablespoons to a "healthy" salad turns it from a 200-calorie side dish into a 440-calorie meal. Similarly, sugary beverages, fruit juices, specialty coffee drinks, and alcohol can contribute hundreds of "invisible" calories that are easily overlooked. Liquid calories are particularly problematic because they don't trigger the same satiety signals as solid food, making it easy to consume 500+ calories from drinks without feeling full.
Neglecting to update your calorie targets as your weight changes leads to plateaus. If you start at 90 kg with a TDEE of 2,800 calories and lose 5 kg, your new TDEE may be around 2,600 calories. If you continue eating 2,300 calories (your original deficit), you're now only in a 300-calorie deficit instead of 500, and your rate of weight loss will slow accordingly. Recalculating your TDEE every 5–10 kg of weight change, or whenever your rate of progress stalls for more than two weeks, helps maintain consistent results.
Your daily caloric intake is composed of three primary macronutrients — proteins, carbohydrates, and fats — each playing a distinct and essential role in your body. Proteins provide 4 calories per gram and serve as the building blocks for muscle tissue, enzymes, hormones, and immune cells. The amino acids in protein are critical for tissue repair, muscle synthesis, and maintaining lean body mass, especially during weight loss. Common protein sources include chicken, fish, eggs, dairy, legumes, tofu, and whey supplements. Most health organizations recommend that protein comprise 10–35% of total daily calories, though higher intakes (25–35%) are beneficial during calorie restriction to preserve muscle.
Carbohydrates provide 4 calories per gram and are the body's preferred and most efficient energy source, particularly for the brain and muscles during high-intensity exercise. Carbohydrates are classified as simple (sugars) or complex (starches and fiber). Complex carbohydrates from whole grains, vegetables, fruits, and legumes provide sustained energy, fiber for digestive health, and important vitamins and minerals. Simple carbohydrates from added sugars and refined grains cause rapid blood sugar spikes followed by crashes, promoting hunger and overeating. Dietary fiber — a type of complex carbohydrate the body cannot digest — is especially important: it promotes satiety, supports gut health, helps regulate blood sugar, and is associated with reduced risk of heart disease, type 2 diabetes, and certain cancers. The recommended daily fiber intake is 25 grams for women and 38 grams for men, though most adults fall far short of these targets.
Fats provide 9 calories per gram — more than double the energy density of proteins and carbohydrates — and are essential for hormone production, cell membrane structure, vitamin absorption (vitamins A, D, E, and K are fat-soluble), brain function, and insulation. Dietary fats are categorized as saturated (primarily from animal products and tropical oils), unsaturated (monounsaturated from olive oil, avocados, and nuts; polyunsaturated from fatty fish, walnuts, and flaxseeds), and trans fats (artificially created through hydrogenation, now largely banned in many countries). Health guidelines recommend limiting saturated fat to less than 10% of total calories, minimizing trans fats entirely, and emphasizing unsaturated fats, particularly omega-3 fatty acids found in fish, which have anti-inflammatory properties and support cardiovascular health.
The Mifflin-St Jeor equation, published in 1990, is the formula used in this calculator and is currently considered the most accurate estimation formula for resting metabolic rate by the Academy of Nutrition and Dietetics. For men, it calculates RMR as 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 5. For women, the final constant is −161 instead of −5. The equation was developed using data from 498 healthy individuals and has been validated against indirect calorimetry measurements.
Other commonly used formulas include the Harris-Benedict equation (original 1919 version and revised 1984 version), which tends to overestimate RMR by approximately 5% compared to Mifflin-St Jeor. The Katch-McArdle formula takes body fat percentage into account rather than using weight alone, making it more accurate for individuals with significantly above or below average body fat levels. The Cunningham equation is similar to Katch-McArdle and is often preferred for athletic populations. While no formula is perfect, Mifflin-St Jeor provides the best balance of accuracy and practical usability for the general population, as it does not require body fat percentage measurements that many people do not have readily available.
One of the most frustrating phenomena for anyone trying to lose weight is metabolic adaptation, sometimes called "adaptive thermogenesis" or colloquially "starvation mode." When you consistently eat fewer calories than your body burns, your metabolism gradually slows down through several mechanisms. Your resting metabolic rate decreases as your body becomes more metabolically efficient. You lose lean muscle mass (unless you're strength training and eating adequate protein), which reduces the number of calories your body burns at rest. Hormonal changes occur: leptin (the satiety hormone) decreases, making you feel hungrier, while ghrelin (the hunger hormone) increases. Thyroid hormone production may decline, further reducing metabolic rate. Even non-exercise activity thermogenesis (NEAT) — the calories burned through fidgeting, standing, and spontaneous movement — decreases as your body unconsciously conserves energy.
Research shows that metabolic adaptation can reduce your actual energy expenditure by 10–25% below predicted values after prolonged calorie restriction. This is why weight loss inevitably slows over time and why many people experience weight loss plateaus. The most effective strategies to counter metabolic adaptation include: incorporating regular strength training to preserve and build muscle mass, using periodic diet breaks or reverse dieting (gradually increasing calories back to maintenance for 1–2 weeks), ensuring adequate protein intake, getting sufficient sleep, and avoiding overly aggressive calorie deficits (more than 500–750 calories below maintenance). It is also important to recognize that some degree of metabolic adaptation is normal and expected — it does not mean your diet is failing.
Effective calorie tracking requires a systematic approach. Food diary apps such as MyFitnessPal, Cronometer, Lose It!, and FatSecret maintain extensive food databases that allow you to quickly log meals and track macronutrient intake. These apps use barcode scanners to simplify packaged food entry and can estimate calories for restaurant meals and homemade recipes. Food scales are essential for accurate portion measurement — studies consistently show that people significantly underestimate their food portions when relying on visual estimation alone. A digital kitchen scale costs around $10–20 and dramatically improves tracking accuracy.
Meal planning and preparation is another effective strategy: planning meals in advance reduces decision fatigue, makes tracking easier (you log recipes once rather than individual ingredients each time), and reduces the likelihood of impulsive high-calorie food choices. The exchange system is an alternative approach that groups foods into categories (starches, proteins, fats, fruits, vegetables, dairy) and assigns each a specific calorie and macronutrient value, allowing flexible meal construction without counting every calorie. Photo food logging (simply photographing everything you eat) has been shown in research to improve dietary awareness and is a good starting point for people who find detailed tracking too burdensome. Regardless of method, consistency matters more than perfection — even tracking at 80% accuracy provides significantly more insight than not tracking at all.
Myth: "Eating late at night causes weight gain." Your body does not have a clock that tells it to store calories differently after 8 PM. What matters is your total daily caloric intake, not the timing of your meals. Late-night eating can lead to weight gain only because people tend to choose high-calorie, highly palatable snack foods in the evening and may exceed their daily calorie needs. However, if your total calories are within your target, eating at night will not inherently cause more fat storage than eating the same calories earlier in the day.
Myth: "Carbs make you fat." Carbohydrates themselves do not cause weight gain — excess calories from any macronutrient will be stored as fat. Low-carbohydrate diets can be effective for weight loss, but they work primarily by reducing overall calorie intake (protein and fat are more satiating per calorie than many carbohydrate sources) and by reducing water weight (each gram of glycogen stored in muscles holds approximately 3 grams of water). Whole-food carbohydrate sources such as fruits, vegetables, legumes, and whole grains are associated with better long-term health outcomes and are not inherently fattening.
Myth: "You must eat small, frequent meals to boost metabolism." The "thermic effect of food" (calories burned through digestion) is determined by the total amount and composition of food consumed, not by how often you eat. Eating six small meals versus three larger meals with the same total calories produces virtually no difference in metabolic rate. Meal frequency is a matter of personal preference and satiety management, not a metabolic hack. Some people find frequent meals help control hunger; others prefer fewer, larger meals for convenience and satisfaction.
Myth: "Detox diets and cleanses remove toxins and promote weight loss." Your liver and kidneys are highly effective at detoxifying your body without any special diets, juices, or supplements. Most "detox" products are marketing gimmicks with no scientific evidence. Any rapid weight loss from a cleanse is almost entirely water weight and glycogen depletion, which returns as soon as you resume normal eating. Save your money and focus on sustainable, evidence-based dietary patterns instead.
Myth: "All calories are equal." While a calorie is a calorie in the strict thermodynamic sense, the source of those calories significantly affects satiety, hormonal response, nutrient intake, and long-term adherence. 200 calories from almonds (protein, fiber, healthy fats) will keep you full far longer than 200 calories from soda (pure sugar with no nutritional value). The quality of your calories matters for health, satiety, and sustainability, even if the quantity is what ultimately determines weight gain or loss.
This calculator uses the Mifflin-St Jeor equation, which is widely regarded as the most accurate BMR estimation formula for the general population. Published in 1990, it has been validated in numerous studies and is recommended by the Academy of Nutrition and Dietetics. The formula differs slightly for men (BMR = 10 × weight in kg + 6.25 × height in cm − 5 × age − 161 + 166, effectively 10W + 6.25H − 5A + 5) and women (BMR = 10 × weight in kg + 6.25 × height in cm − 5 × age − 161). Your BMR is then multiplied by an activity factor ranging from 1.2 (sedentary) to 1.9 (very active) to calculate your TDEE. While no formula is perfect, Mifflin-St Jeor typically estimates within 10% of actual measured metabolic rates.
The calorie targets provided are solid estimates based on well-established nutritional science, but individual results will vary. Metabolic adaptation (often called "adaptive thermogenesis") means your body may gradually reduce its calorie burn in response to a sustained deficit, causing weight loss to slow over time. Factors like genetics, gut microbiome composition, sleep quality, stress levels, and hormonal status all influence how your body responds to a given calorie intake. The calculator gives you an excellent starting point, but you should monitor your actual results over 2–4 weeks and adjust your intake up or down by 100–200 calories if progress is faster or slower than expected.
Not necessarily. Calorie tracking is most valuable as an educational tool that helps you understand portion sizes, macronutrient composition, and how different foods affect your satiety and energy levels. Many people find that after 4–8 weeks of consistent tracking, they develop an intuitive sense of appropriate portion sizes and can transition to a more relaxed approach. However, if you have specific physique goals (like competition preparation) or are struggling to make progress, returning to tracked periods can help identify where your intake may have drifted. The goal of this calculator is to empower you with knowledge, not to create a lifelong obsession with numbers.