# Calorie & Protein Calculator Most adult women maintain their weight on about 1,600 to 2,400 kcal a day and most adult men on about 2,000 to 3,000 kcal, depending on age, body size and activity. This tool estimates your own maintenance calories (TDEE) with the Mifflin-St Jeor equation, then shows a moderate fat-loss deficit (about 300 to 500 kcal a day, roughly 0.5 to 1.0% of bodyweight a week) and a protein range of 1.6 to 2.2 g per kg of bodyweight associated with protecting muscle. The numbers are rough starting points, not promises: your real burn varies and adapts, so people typically watch their results over two to three weeks and adjust. ## How this calculator works Five quick inputs, three useful numbers. Here is what happens under the hood. - You enter your sex, age, height, weight, activity level, and goal. - We estimate your resting metabolism with the Mifflin-St Jeor equation [1], among the best-validated resting-energy formulas for healthy adults [2]. - We multiply that by an activity factor to estimate your maintenance calories, the total you burn on an average day. - For fat loss we subtract a moderate deficit (about 300 to 500 kcal) and show the estimated weekly loss, because losing at roughly 0.5 to 1.0% of bodyweight a week protects muscle [6]. - The tool shows a protein range of 1.6 to 2.2 g per kg, the band the research associates with muscle retention during weight loss [3, 4]. ## How many calories do I need a day? Most adult women maintain their weight on roughly 1,600 to 2,400 kcal a day and most adult men on roughly 2,000 to 3,000 kcal, depending on age, body size and daily movement [18]. Those population ranges hide a large individual spread, which is why a calculated estimate beats any generic rule: this calculator estimates your personal maintenance from your sex, age, height, weight and activity, then shows what to eat for fat loss (a 300 to 500 kcal deficit) or muscle gain (a small surplus). To lose weight you eat below maintenance; many women land near 1,400 to 1,900 kcal a day and many men near 1,700 to 2,500, but your own number can sit well outside those bands, so calculate rather than copy an average. ## How big a deficit should you use? In the research, a moderate deficit of roughly 300 to 500 kcal a day lands near 0.5 to 1.0% of bodyweight a week [6]. In a trial of athletes who trained hard and ate plenty of protein, losing at about 0.7% a week preserved and even built muscle, while losing twice as fast did not [7]. Leaner people tend to do better at the slower end of that range; people carrying more fat often tolerate the faster end. Cutting harder rarely speeds real fat loss in the evidence; it mostly costs muscle and makes the diet harder to sustain. ## How much protein do you need while losing weight? Protein is what keeps the weight you lose coming off as fat, not muscle. A sports-nutrition consensus puts the useful range for active people at 1.4 to 2.0 g per kg of bodyweight [3], and meta-analyses place the point of diminishing returns for muscle near 1.6 g per kg, with little extra benefit beyond about 2.2 g per kg [4, 15]. Reviews of lean dieters who train go higher still, to 2.3 to 3.1 g per kg of fat-free mass [5]. For most active people the research points to 1.6 to 2.2 g per kg as a well-supported range, applied to a reference weight (your height at a healthy BMI) rather than raw bodyweight, so it isn't overstated if you carry extra fat; with a known body-fat % the advanced option bases it on lean mass instead. For a more detailed breakdown, our protein calculator covers the same ground. ## The formula, in the open Your resting metabolism uses the Mifflin-St Jeor equation [1]. For men: 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5. For women: the same, minus 161. We multiply that by an activity factor (1.2 sedentary to 1.9 very active) to estimate maintenance. We use Mifflin-St Jeor rather than the older Harris-Benedict (1919) because it is more accurate for today's bodies [2]. If you have cross-checked elsewhere and got a higher number, that older formula is usually why. Enter a body-fat % in the advanced options and we switch to Katch-McArdle instead: 370 + 21.6 × lean mass. ## Mifflin-St Jeor vs. Harris-Benedict vs. Katch-McArdle: which formula is most accurate? Mifflin-St Jeor (1990) is the default here because validation work rates it the most reliable of the common equations for healthy adults, predicting measured resting metabolism within about 10% for the largest share of people [2]. Harris-Benedict (1919, revised 1984) was built on a small, century-old sample and tends to overestimate for today's bodies by roughly 5%, which is why other calculators often hand you a higher number. Katch-McArdle works from lean body mass instead of total weight, so it can beat both for very lean or very muscular people, but only when the body-fat percentage you feed it is trustworthy (DEXA or calipers, not a glance in the mirror). Rule of thumb: without a reliable body-fat measurement use Mifflin-St Jeor; with one, Katch-McArdle. ## What is the difference between BMR, maintenance calories and TDEE? Your resting metabolic rate (BMR, or basal metabolic rate) is what your body burns at complete rest. Your activity burn is everything on top: walking, training, fidgeting, digesting. Maintenance, also called total daily energy expenditure (TDEE), is the two added together: BMR × an activity factor. Eat around maintenance to hold your weight, below it to lose fat, above it to build muscle. The activity factor is the biggest lever and the biggest source of error, which is why the advanced options show maintenance at every level at once. ## These are estimates, so treat them that way Every formula here is a population average, and your real burn can sit above or below it, especially at the extremes of body size and in older adults. The weekly-loss figures use a simple rule of thumb (about 7,700 kcal per kg of fat); real loss is slower and tapers as your body adapts; a maintained 500 kcal/day cut delivers only about half its 'expected' loss in the first year [13], so treat the weekly number as a four-to-eight-week guide, not a promise [10, 11]. For multi-month projections, the NIH Body Weight Planner models the slowdown. Metabolism may also adapt after weight loss, with resting energy expenditure dropping by somewhat more than your smaller body explains, though how large and lasting that is remains debated [8]; and after about 60, estimates get less precise as cellular metabolism declines independent of muscle and movement [14]. The remedy isn't a fancier equation, it's feedback. In practice, people treat the number as a hypothesis: holding intake near the estimate for two to three weeks, watching the weekly-average weight, and revising by roughly 100 to 200 kcal if the trend is off. A dietitian can help you do this safely. ## FAQ ### How accurate is a calorie calculator? It gives a solid starting estimate, usually within about 10% for most healthy adults, but it is still an estimate. The Mifflin-St Jeor equation it uses [1] is among the best-validated for resting metabolism [2], though it is less accurate at the extremes of body size and less well validated in older adults. Your true burn also depends on genetics, muscle mass, and daily movement, so use the number as a starting point and adjust based on your weekly results. ### What is the difference between BMR and maintenance calories? BMR (basal metabolic rate) is what your body burns at complete rest just to keep you alive. Maintenance, or TDEE, is BMR plus everything else you do: walking, fidgeting, working out, digesting food. We multiply BMR by an activity factor to estimate maintenance, the number you eat around to hold your weight. ### How big a calorie deficit should I use to lose fat? A moderate one, about 300 to 500 kcal a day, which is roughly 0.5 to 1.0% of bodyweight a week [6]. Losing slower protects muscle: in one trial, the slower rate built muscle (alongside strength training) while the faster rate did not [7]. We never suggest eating below your resting metabolism. ### How much protein should I eat while losing weight? About 1.6 to 2.2 g per kg of bodyweight a day if you train [4]. A sports-nutrition consensus sets 1.4 to 2.0 g per kg as a solid floor [3], and reviews of lean dieters go to 2.3 to 3.1 g per kg of fat-free mass [5]. For people with a lot of body fat, the research applies the range to a realistic goal weight rather than current bodyweight so the target isn't overstated. ### Why does my weight loss slow down even if I keep eating the same? Two things compound: maintenance drops as you get smaller, and resting metabolism can fall by somewhat more than your size predicts (adaptive thermogenesis), though its size is debated [8]. People typically recalculate as their weight changes and keep protein and resistance training high to protect muscle; our weight-loss plateau guide covers the evidence. ### Is the 7,700 kcal per kg (3,500 kcal) weight-loss rule accurate? It is a handy short-term guide but it overestimates real loss over months. A maintained 500 kcal/day deficit delivers only about half its 'expected' loss in the first year as your body adapts [13]. Use the weekly figure as a four-to-eight-week guide, not a six-month promise; for longer projections the NIH Body Weight Planner models the slowdown. ### Which formula is most accurate: Mifflin-St Jeor or Harris-Benedict? For most healthy adults Mifflin-St Jeor (1990) is the more accurate of the common equations, landing within about 10% of measured resting metabolism [2]. The older Harris-Benedict (1919) tends to run higher, which is why other calculators may show you a larger number. If you know your body-fat %, Katch-McArdle can be better still for very lean or muscular people because it works from lean mass. ### Does my menstrual cycle or menopause change my calorie needs? Only a little. Resting metabolism rises modestly in the second half of the cycle, usually under 60 kcal a day, which sits inside this tool's margin, so we don't add a cycle adjustment. Menopause needs no separate factor either: the decline tracks age and lean mass, which are already inputs [14]. Pregnancy and breastfeeding do add real needs (roughly +250 and +500 kcal under medical guidance) and are outside this tool's scope. ### What is a safe minimum number of calories per day? This tool never suggests eating below your resting metabolism, and holds a lower bound of 1,200 kcal for women and 1,500 for men [12]. Diets below about 800 kcal a day are clinical very-low-calorie diets that need medical supervision (NICE NG246, 2025). If hitting a number ever feels distressing, please speak to a doctor. ### Why does every calorie calculator show me a different number? Three reasons: different formulas (Harris-Benedict runs about 5% higher than Mifflin-St Jeor), different activity multipliers (many tools compress your whole life into one vague dropdown, this one separates your job baseline from your training), and rounding. Differences of 100 to 300 kcal between tools are normal, and no formula beats the roughly ±10% real-world spread anyway [2]. Pick one estimate, hold it for two to three weeks, and let your weekly-average weight tell you whether to adjust. ### How many calories does the average person need a day? The usual label reference is 2,000 kcal for women and 2,500 kcal for men, but real maintenance runs roughly 1,600 to 2,400 kcal for adult women and 2,000 to 3,000 kcal for adult men depending on age, size and movement [18]. A small office worker and a tall nurse can differ by 1,000 kcal a day, which is why this calculator asks for your details instead of assuming an average. ### Should I eat back the calories I burn from exercise? With this calculator, no: your training is already averaged into your daily target, that is what the exercise inputs do. Eating workout calories back on top would count them twice. Treat watch and machine readouts with suspicion too; planned workouts often displace other daily movement, so the true net extra is smaller than the display suggests. ## Sources - Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. (1990). A new predictive equation for resting energy expenditure in healthy individuals. The American Journal of Clinical Nutrition. https://doi.org/10.1093/ajcn/51.2.241 - Frankenfield D, Roth-Yousey L, Compher C. (2005). Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. Journal of the American Dietetic Association. https://doi.org/10.1016/j.jada.2005.02.005 - Jäger R, Kerksick CM, Campbell BI, Cribb PJ, Wells SD, Skwiat TM, et al.. (2017). International Society of Sports Nutrition Position Stand: protein and exercise. Journal of the International Society of Sports Nutrition. https://doi.org/10.1186/s12970-017-0177-8 - Morton RW, Murphy KT, McKellar SR, Schoenfeld BJ, Henselmans M, et al.. (2018). A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. British Journal of Sports Medicine. https://doi.org/10.1136/bjsports-2017-097608 - Helms ER, Zinn C, Rowlands DS, Brown SR. (2014). A systematic review of dietary protein during caloric restriction in resistance trained lean athletes: a case for higher intakes. International Journal of Sport Nutrition and Exercise Metabolism. https://doi.org/10.1123/ijsnem.2013-0054 - Aragon AA, Schoenfeld BJ, Wildman R, Kleiner S, VanDusseldorp T, et al.. (2017). International Society of Sports Nutrition position stand: diets and body composition. Journal of the International Society of Sports Nutrition. https://doi.org/10.1186/s12970-017-0174-y - Garthe I, Raastad T, Refsnes PE, Koivisto A, Sundgot-Borgen J. (2011). Effect of two different weight-loss rates on body composition and strength and power-related performance in elite athletes. International Journal of Sport Nutrition and Exercise Metabolism. https://doi.org/10.1123/ijsnem.21.2.97 - Leibel RL, Rosenbaum M, Hirsch J. (1995). Changes in energy expenditure resulting from altered body weight. New England Journal of Medicine. https://doi.org/10.1056/NEJM199503093321001 - Paluch AE, Bajpai S, Bassett DR, Carnethon MR, Ekelund U, et al.. (2022). Daily steps and all-cause mortality: a meta-analysis of 15 international cohorts. The Lancet Public Health. https://doi.org/10.1016/S2468-2667(21)00302-9 - Wishnofsky M. (1958). Caloric equivalents of gained or lost weight. The American Journal of Clinical Nutrition. https://doi.org/10.1093/ajcn/6.5.542 - Hall KD, Chow CC. (2013). Why is the 3500 kcal per pound weight loss rule wrong?. International Journal of Obesity. https://doi.org/10.1038/ijo.2013.112 - Jensen MD, Ryan DH, Apovian CM, Ard JD, Comuzzie AG, et al.. (2014). 2013 AHA/ACC/TOS Guideline for the Management of Overweight and Obesity in Adults. Circulation. https://doi.org/10.1161/01.cir.0000437739.71477.ee - Hall KD, Sacks G, Chandramohan D, Chow CC, Wang YC, Gortmaker SL, Swinburn BA. (2011). Quantification of the effect of energy imbalance on bodyweight. The Lancet. https://doi.org/10.1016/S0140-6736(11)60812-X - Pontzer H, Yamada Y, Sagayama H, Ainslie PN, Andersen LF, et al.. (2021). Daily energy expenditure through the human life course. Science. https://doi.org/10.1126/science.abe5017 - Nunes EA, Colenso-Semple L, McKellar SR, Yau T, Ali MU, et al.. (2022). Systematic review and meta-analysis of protein intake to support muscle mass and function in healthy adults. Journal of Cachexia, Sarcopenia and Muscle. https://doi.org/10.1002/jcsm.12922 - Murphy C, Koehler K. (2022). Energy deficiency impairs resistance training gains in lean mass but not strength: A meta-analysis and meta-regression. Scandinavian Journal of Medicine & Science in Sports. https://doi.org/10.1111/sms.14075 - Barakat C, Pearson J, Escalante G, Campbell B, De Souza EO. (2020). Body Recomposition: Can Trained Individuals Build Muscle and Lose Fat at the Same Time?. Strength and Conditioning Journal. https://doi.org/10.1519/SSC.0000000000000584 - Institute of Medicine, Food and Nutrition Board. (2005). Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. National Academies Press. https://doi.org/10.17226/10490 - Ainsworth BE, Haskell WL, Herrmann SD, Meckes N, Bassett DR, et al.. (2011). 2011 Compendium of Physical Activities: a second update of codes and MET values. Medicine & Science in Sports & Exercise. https://doi.org/10.1249/MSS.0b013e31821ece12 _Full tool: https://longevity-switzerland.com/en/tools/calorie-calculator_ --- _Canonical: https://longevity-switzerland.com/en/tools/calorie-calculator · Part of Longevity Cities_