Calorie Calculator
Find your Basal Metabolic Rate (BMR), Total Daily Energy Expenditure (TDEE), and a goal-based daily calorie target using the Mifflin-St Jeor equation — the formula most dietitians consider the most reliable for the general population. Get a full macronutrient breakdown, with a built-in safety floor so you're never pointed toward an unsafe calorie level.
- Mifflin-St Jeor equation
- Metric & imperial
- Macronutrient breakdown
- Safety floor built in
- Shareable results
Calorie calculator inputs and results
What is BMR (Basal Metabolic Rate)?
Your Basal Metabolic Rate is the number of calories your body burns at complete rest to keep essential systems running — breathing, circulating blood, regulating body temperature, and repairing cells. It's the energy cost of simply being alive, measured under conditions of total physical and digestive rest. BMR typically accounts for 60% to 75% of total daily calorie burn for most people, making it the single largest piece of your energy budget.
What is TDEE (Total Daily Energy Expenditure)?
TDEE takes your BMR and adds everything else your body burns across a normal day: digesting food, moving around, and any structured exercise. TDEE is always higher than BMR, and it represents your true maintenance calorie level — eat exactly your TDEE and your weight should, on average, stay stable over time. This calculator estimates TDEE by multiplying your BMR by an activity factor that reflects your typical weekly routine.
How the Mifflin-St Jeor equation works
Published in 1990 and validated against measured energy expenditure in thousands of participants, the Mifflin-St Jeor equation has become the standard BMR formula recommended by the Academy of Nutrition and Dietetics, replacing the older Harris-Benedict equation, which tends to overestimate BMR for most modern populations. It uses weight, height, and age, with a fixed constant that differs by sex to account for average differences in lean body mass.
For imperial inputs, this calculator first converts pounds to kilograms (1 lb = 0.453592 kg) and feet and inches to centimeters (1 ft = 30.48 cm, 1 in = 2.54 cm), then runs the exact same formula — so your result is identical regardless of which unit system you use.
A worked walkthrough
Consider a 32-year-old woman who is 170 cm tall, weighs 68 kg, exercises lightly three days a week, and wants to lose weight at a moderate pace. Her BMR works out to 1,421.5 kcal/day using the formula above. Multiplying by the lightly active factor of 1.375 gives a TDEE of roughly 1,955 kcal/day — the calories she'd need to maintain her current weight. Selecting "Weight loss" applies a 500 kcal deficit, producing a target of about 1,455 kcal/day, which sits above her 1,200 kcal safety floor, so no warning is triggered. At that deficit, she can expect to lose approximately 0.45 kg (1 lb) a week on average, and her macronutrient breakdown at the default 40/30/30 split works out to roughly 146 g of carbohydrate, 109 g of protein, and 48 g of fat per day.
Now compare that to choosing "Fast weight loss" instead, which applies a 1,000 kcal deficit. That would put her target at 955 kcal/day — well below the 1,200 kcal floor — so this calculator automatically raises it back to 1,200 kcal/day and displays a warning explaining why, rather than silently recommending an unsafe number.
Customizing your macronutrient split
The default 40% carbohydrate, 30% protein, 30% fat split works well as a general-purpose starting point for most goals, but it isn't the only reasonable approach. Endurance athletes often benefit from a higher carbohydrate share to fuel training volume, while some people pursuing fat loss prefer a higher protein share, sometimes up to 35% of calories, to maximize satiety and muscle preservation during a deficit. As long as protein intake stays adequate (a common guideline is roughly 1.6 to 2.2 g per kilogram of body weight for active adults) and total calories match your target, the exact carbohydrate-to-fat ratio can be adjusted to fit your preferences and how different foods make you feel, without changing the underlying calorie math this calculator provides.
Understanding activity levels
Once BMR is known, it's multiplied by an activity factor to estimate TDEE. Sedentary (factor 1.2) fits someone with a desk job and little deliberate exercise. Lightly active (1.375) fits light exercise or sports one to three days a week. Moderately active (1.55) fits moderate exercise three to five days a week. Very active (1.725) fits hard exercise six to seven days a week. Extra active (1.9) fits very hard daily training combined with a physically demanding job, such as a construction worker who also trains intensely. Choosing accurately matters — overestimating activity is one of the most common reasons people plateau despite "eating in a deficit."
How a calorie deficit leads to weight loss
Weight loss follows from energy balance: when you consistently consume fewer calories than your body uses, it draws on stored energy, primarily fat tissue, to cover the gap. Because roughly 3,500 kcal of stored energy corresponds to about one pound (0.45 kg) of body fat, a sustained daily deficit of 500 kcal produces, on average, about one pound of loss per week. This calculator applies that same math to translate your goal into a concrete daily calorie target.
How a calorie surplus leads to weight gain
The same logic runs in reverse for weight gain: consuming more energy than you burn provides surplus calories that the body can store as new tissue. A moderate surplus of around 300 to 500 kcal a day, paired with resistance training, is generally favored for building muscle with a more favorable ratio of muscle to fat gain than a larger, faster surplus, which tends to add more fat relative to muscle.
Safe rate of weight loss
Most public health guidelines consider a rate of 0.5 to 1 kg (about 1 to 2 lb) per week a safe, sustainable pace for the majority of adults carrying excess weight, achieved through a deficit of roughly 500 to 1,000 kcal a day. Faster loss is sometimes appropriate briefly under medical supervision, but sustained very low-calorie eating raises the risk of muscle loss, nutrient deficiency, gallstones, and a slowed metabolic rate, along with a higher likelihood of regaining the weight afterward.
Why restrictive diets can be dangerous
Diets that push calorie intake far below BMR, or that eliminate entire food groups, can trigger a cascade of problems: inadequate protein intake accelerates muscle loss during weight loss, very low-calorie intake disrupts hormones that regulate hunger and metabolism, and severe restriction is a known risk factor for disordered eating patterns. This calculator enforces a floor of 1,200 kcal/day for women and 1,500 kcal/day for men and displays a clear warning if your goal would otherwise fall below it — these floors reflect commonly cited clinical minimums for unsupervised dieting, not a target to aim for.
The importance of macronutrients
Calories set the overall size of the energy budget, but the mix of protein, carbohydrate, and fat within that budget shapes how you feel and what your body does with the calories. Protein (4 kcal/g) supports muscle repair and preservation, particularly important during a calorie deficit, and is the most satiating macronutrient per calorie. Carbohydrates (4 kcal/g) are the body's preferred fuel for higher-intensity exercise and brain function. Fat (9 kcal/g) supports hormone production and the absorption of fat-soluble vitamins. This calculator applies a balanced default split of 40% carbohydrate, 30% protein, and 30% fat, converting your target calories into grams for each.
Limitations of calorie calculators
Every BMR formula, including Mifflin-St Jeor, is a population-level estimate built from averages — it does not measure your actual metabolism, which can vary meaningfully based on genetics, muscle mass, thyroid function, medications, and even sleep quality. Studies generally show Mifflin-St Jeor predicts measured resting energy expenditure within about 10% for most people, which is good accuracy for a formula requiring no lab equipment, but it is still an estimate, not a measurement. Treat your calculated target as a well-informed starting point to test and adjust over two to three weeks based on your real-world results, not a fixed, permanent number.
Why individual variation matters
Two people of identical height, weight, age, and sex can have meaningfully different metabolic rates due to differences in muscle mass (muscle burns more calories at rest than fat tissue), genetics, hormone levels including thyroid function, and even the composition of gut bacteria, which influences how efficiently food energy is extracted. If your real-world weight trend consistently diverges from what this calculator predicts after a few weeks of accurate tracking, trust the trend and adjust your target rather than the formula.
Metabolic adaptation and weight-loss plateaus
As weight decreases, TDEE naturally falls too, for two compounding reasons: a lighter body simply requires fewer calories to move and maintain, and sustained dieting can trigger a modest additional slowdown in metabolic rate beyond what weight loss alone would predict, an effect researchers call adaptive thermogenesis. This is why a calorie target that worked well in week one often stops producing the same results by week eight — it isn't a sign anything has gone wrong, just a signal to recalculate your target against your new weight, or to introduce a short maintenance break before continuing a deficit.
Calorie needs for athletes and highly active individuals
Athletes and very physically active people often need meaningfully more calories than standard activity-factor estimates suggest, particularly during heavy training blocks, and typically benefit from a higher protein intake than the general population to support recovery and muscle repair. The "extra active" setting in this calculator is a reasonable starting point for very high training volumes, but competitive athletes are often best served by working with a sports dietitian who can account for training periodization, body composition goals, and event-specific fueling needs.
Calorie needs for older adults
BMR gradually declines with age, primarily due to a natural loss of muscle mass over time, which means calorie needs for maintaining the same weight typically fall gradually across adulthood even when activity level stays constant. Preserving muscle mass through resistance training and adequate protein intake becomes increasingly important with age, both for metabolic health and for maintaining strength and mobility. This calculator's age input automatically adjusts for this in the underlying formula.
Why children and teenagers need different calculations
This calculator is built for adults aged 18 and over. Children and teenagers are still growing, and their calorie needs must support that growth in addition to daily activity, which the Mifflin-St Jeor equation — designed and validated for adults — does not account for. Calorie and nutrition planning for anyone under 18 should be guided by a pediatrician or registered dietitian familiar with growth-stage nutrition needs.
Weight management tips
Diet
Prioritize protein at each meal
Adequate protein helps preserve muscle during a deficit and tends to be the most filling macronutrient, making a calorie target easier to sustain.
Track loosely, not obsessively
Logging food for a couple of weeks builds useful awareness of portion sizes without needing to continue indefinitely once the patterns feel intuitive.
Fill up on volume foods
Vegetables and other high-volume, lower-calorie-density foods help you feel full on fewer calories than energy-dense processed options.
Plan for flexibility
Building in room for occasional treats or social meals tends to produce more consistent long-term adherence than an all-or-nothing approach.
Exercise
Keep resistance training in the mix
Strength training helps preserve muscle mass during a deficit and supports muscle growth during a surplus — both protect your metabolic rate over time.
Don't over-credit exercise calories
Calorie burn estimates from wearables and machines are often inflated; treating them as rough guidance rather than exact numbers avoids inadvertently under-eating.
Build in recovery
Adequate rest between hard training sessions supports the adaptations that make exercise effective in the first place.
Increase daily movement
Non-exercise activity like walking meaningfully adds to total calorie burn and is often easier to sustain long term than extra formal workouts.
Lifestyle
Protect your sleep
Poor sleep is consistently linked to increased hunger and cravings, which can make a calorie target harder to hit regardless of willpower.
Manage stress
Chronic stress affects appetite-regulating hormones — short daily practices like walking or breathing exercises can help keep it in check.
Reassess every few weeks
As your weight changes, so does your BMR — recalculating periodically keeps your target aligned with your current body rather than your starting point.
Involve a professional for bigger changes
A registered dietitian can personalize targets far beyond what any calculator can, especially alongside medical conditions or medications.
Common calorie-tracking mistakes
Underestimating portion sizes
Eyeballing portions instead of weighing or measuring food is one of the most common sources of error, and small daily underestimates compound into a stalled deficit over weeks.
Forgetting cooking oils and condiments
Oils, dressings, and sauces are calorie-dense and easy to under-log, often adding several hundred uncounted calories a day without much volume or visible bulk.
Overcorrecting after one bad day
A single high-calorie day or missed workout doesn't undo weeks of consistent progress — dramatically cutting calories the next day tends to backfire more than it helps.
Chasing the scale daily
Day-to-day weight fluctuates with water retention, sodium, and hormones; a weekly or rolling average is a far more reliable signal than any single morning's number.
Never recalculating as weight changes
Your TDEE shifts as your body weight changes, so a target calculated at the start of a diet gradually becomes too high without a periodic recheck.
Confusing "clean eating" with calorie control
Whole, minimally processed foods matter for nutrient quality, but calories still count regardless of source — it's possible to overeat calories from entirely healthy foods.
How exercise interacts with your calorie target
Resistance training doesn't just burn calories during the session — it also helps preserve the muscle mass that keeps your BMR from falling further than expected during a deficit, and it provides the mechanical stimulus muscle needs to grow during a surplus. Cardiovascular exercise burns calories more directly and supports heart health, but on its own, without adequate protein and some strength work, a chunk of any weight lost during a deficit can come from muscle rather than fat. For most people balancing a physique and health goal, a mix of two to four resistance sessions a week alongside whatever cardio they enjoy tends to outperform either approach alone.
Choosing between mild, standard, and fast weight loss
The three loss speeds this calculator offers trade off convenience against comfort in different ways. Mild weight loss (a 250 kcal deficit, roughly 0.25 kg or 0.5 lb a week) is the easiest to sustain for long stretches, keeps hunger manageable, and preserves the most muscle and training performance, making it a good fit for people with a smaller amount to lose or a slower timeline. Standard weight loss (a 500 kcal deficit, roughly 0.5 kg or 1 lb a week) is the pace most commonly recommended by health authorities, balancing a reasonable timeline with sustainability for most adults. Fast weight loss (a 1,000 kcal deficit, roughly 1 kg or 2 lb a week) produces the quickest results but is harder to sustain, carries a higher risk of muscle loss, and is most appropriate for short, defined stretches rather than an entire weight-loss journey — this calculator's safety floor exists specifically because this setting is the one most likely to push a target too low.
A practical approach many people find effective is starting with the standard pace, monitoring results over two to three weeks, and adjusting only if progress notably stalls or moves faster than expected — rather than picking the fastest option by default and hoping to sustain it indefinitely.
Key terms explained
- BMR
- Basal Metabolic Rate — the calories your body burns at complete rest to sustain essential functions.
- TDEE
- Total Daily Energy Expenditure — BMR plus digestion, daily movement, and exercise; your true maintenance calorie level.
- Calorie deficit
- Consuming fewer calories than TDEE, prompting the body to draw on stored energy and lose weight over time.
- Calorie surplus
- Consuming more calories than TDEE, providing extra energy the body can store as new tissue, including muscle when paired with training.
- Macronutrients
- The three calorie-providing nutrients — protein, carbohydrate, and fat — each with a distinct role in energy, recovery, and health.
- Activity factor
- A multiplier applied to BMR to estimate TDEE, based on how much structured and incidental activity you do in a typical week.
Medical disclaimer
This calculator is for general informational and educational purposes only and does not constitute medical or nutritional advice, diagnosis, or treatment. It is not intended for pregnant or breastfeeding individuals, anyone under 18, or people with a history of disordered eating. Always consult a doctor or registered dietitian before making significant changes to your diet or exercise routine, particularly if you have an existing health condition.
Frequently asked questions
Answers to the questions people ask most often about calorie needs, BMR, TDEE, and safe weight management.
A calorie deficit means consistently eating fewer calories than your body burns in a day, which forces it to draw on stored energy, primarily body fat, to make up the difference. A deficit of roughly 500 calories a day, sustained over a week, typically produces about one pound (0.45 kg) of weight loss, since a pound of body fat holds approximately 3,500 calories of stored energy.
Most people lose weight safely and sustainably by eating roughly 500 calories below their Total Daily Energy Expenditure (TDEE), which this calculator estimates for you based on your height, weight, age, sex, and activity level. Eating far below TDEE can speed short-term loss but often isn't sustainable and can affect energy, mood, and muscle mass, which is why this calculator enforces a safety floor.
Basal Metabolic Rate (BMR) is the number of calories your body needs at complete rest just to keep essential functions running, such as breathing, circulation, and cell repair. It matters because it forms the foundation of your total calorie needs — every other activity throughout the day adds calories on top of this baseline.
The Mifflin-St Jeor equation is widely regarded by dietitians and researchers as the most accurate BMR formula available for the general population, typically predicting resting energy expenditure within about 10% of measured values. No formula is perfectly precise for every individual, since factors like muscle mass, genetics, and hormone levels also influence metabolism.
Choose the activity level that reflects your typical week, not your best week: sedentary means little to no structured exercise, lightly active covers light exercise one to three days a week, moderately active covers three to five days, very active covers hard exercise six to seven days a week, and extra active covers very hard daily training combined with a physically demanding job. Most desk-based workers with a few weekly workouts fall into lightly or moderately active.
Yes — selecting the weight gain goal applies a moderate calorie surplus on top of your TDEE, which provides the extra energy needed to support muscle growth when combined with resistance training and adequate protein intake. Muscle gain also depends heavily on training stimulus and protein intake, which this calculator's macronutrient breakdown can help guide.
Most health authorities consider a rate of about 0.5 to 1 kg (roughly 1 to 2 lb) per week to be a safe, sustainable pace for most adults, achieved through a moderate calorie deficit. Faster loss is sometimes appropriate under medical supervision, but unsupervised very low-calorie diets carry higher risk of muscle loss, nutrient deficiency, and rebound weight regain.
It depends on how your activity level was estimated. If you selected an activity level that already reflects your typical exercise routine, your TDEE already accounts for that movement, and you generally shouldn't add exercise calories back on top. If you chose sedentary and then did an unusually intense workout, eating back a portion of those calories can help avoid an unintentionally large deficit.
This calculator is built for adults aged 18 and over. Teenagers are still growing, and their calorie and nutrient needs are assessed differently to support healthy development — a pediatrician or registered dietitian should guide calorie targets for anyone under 18.
This calculator is not designed for pregnancy or breastfeeding, both of which significantly increase calorie and nutrient needs in ways a general formula doesn't account for. Please consult an obstetrician, midwife, or registered dietitian for calorie and nutrition guidance during pregnancy or while breastfeeding.
BMR is the energy your body needs at complete rest, while TDEE adds everything else on top: digestion, daily movement, and exercise. TDEE is always higher than BMR and represents your true maintenance calorie level — the number most people actually need for day-to-day planning.
The Mifflin-St Jeor equation uses a different constant for men and women because, on average, men carry more lean muscle mass at the same body weight, which raises resting energy expenditure. This is a population-level statistical adjustment built into the formula, not a personal judgment about your body.
The Mifflin-St Jeor equation adds 5 for men and subtracts 161 for women after the shared weight, height, and age terms, a difference of 166 calories that reflects average differences in lean body mass between sexes at a population level. Individuals of either sex with above-average muscle mass will typically have a higher BMR than the formula predicts.
Very low-calorie diets, generally below about 1,200 calories a day for women or 1,500 for men, increase the risk of nutrient deficiencies, muscle loss, fatigue, and a slowed metabolism, and are typically only recommended under medical supervision. This calculator automatically raises any target that falls below these floors and displays a clear warning.
Your maintenance calories are your TDEE — the estimated number of calories your body burns in a typical day given your height, weight, age, sex, and activity level. Selecting "Maintain weight" as your goal in this calculator sets your target equal to your TDEE.
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