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The Mifflin-St Jeor equation estimates resting calorie burn from weight, height, age and sex; multiplying by an activity factor gives TDEE (total daily energy expenditure). Your goal applies a moderate adjustment (lose −15%, maintain TDEE, gain +15%, build muscle +10%), and macros split the target into protein (1.4–1.6 g/kg), fat (~30%) and remaining carbs. Results are estimates for planning, not professional medical advice.
This calculator uses the Mifflin–St Jeor equation, regarded as the most accurate of the common BMR formulas, followed by an activity multiplier. There are two steps.
Step 1, Basal Metabolic Rate (BMR), the energy you burn at complete rest: for men, BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5; for women, the last term is − 161 instead of + 5.
Step 2, Total Daily Energy Expenditure (TDEE) = BMR × activity factor. The standard multipliers are: sedentary 1.2, light activity 1.375, moderate 1.55, very active 1.725, extra active 1.9.
Worked example, a 27-year-old woman, 62 kg, 180 cm, moderately active: BMR = (10 × 62) + (6.25 × 180) − (5 × 27) − 161 = 620 + 1,125 − 135 − 161 = 1,449 kcal/day. TDEE = 1,449 × 1.55 = 2,246 kcal/day. That is her estimated maintenance level: eat around 2,246 to keep weight stable, below it to lose, above it to gain.
Enter your age, sex, weight in kilograms and height in centimetres, then pick your activity level, count both planned exercise and how much you move at work. If you are unsure, choose the lower level: overestimating activity inflates your maintenance number and stalls weight loss.
Next choose your goal: lose weight, maintain, gain weight, or build muscle. The calculator shows your daily calorie target plus daily protein, carbohydrate and fat targets in grams, so you know exactly what to eat, not just how much.
These are predictive estimates, not measurements, treat the number as a starting point and adjust it based on how your weight actually moves over two to three weeks.
BMR is the baseline: the energy your body uses at rest to run essential functions such as breathing, circulation and keeping your organs going. TDEE is the number you actually live on: BMR adjusted for your usual activity level, covering everything you do in a day.
Simply put: BMR is what you would burn lying still all day; TDEE estimates what you burn in your real life. That is why calorie targets come from TDEE, not from BMR, eating at your BMR would starve every bit of activity, and most people who do that stall quickly.
The five activity multipliers cover the whole range: sedentary (desk job, little or no exercise) × 1.2, lightly active (1–3 days/week) × 1.375, moderately active (3–5 days/week) × 1.55, very active (6–7 days/week) × 1.725, and extra active (physical job plus hard daily training) × 1.9. Moving one level changes the answer by roughly 200–400 kcal, so pick carefully.
Once you know your maintenance calories (TDEE), your goal decides the target:
Lose weight: a target below maintenance. This calculator applies a moderate 15% deficit as a practical starting point, for a 2,246 kcal maintenance, that is about 1,909 kcal/day. A deficit of roughly 500 kcal/day below maintenance works out to about 0.5 kg (1 lb) of loss per week, since that much body fat holds about 3,500 kcal. The safe range is 250–500 below maintenance; cutting harder risks muscle loss, fatigue and rebound eating.
Maintain: eat around your TDEE, maintenance calories are the estimated daily energy use for keeping your current body weight relatively stable.
Gain weight: a larger surplus above maintenance, about 15%, aimed at increasing overall body weight.
Build muscle: a smaller, controlled surplus of about 10%, with a higher protein estimate, because eating more calories does not automatically create more muscle. Resistance training provides the stimulus; the surplus should build muscle rather than just fat.
The calculator never lets a target drop below 1,200 kcal/day; if it would, it floors the value and shows a safety note, because very low intakes carry health risks.
Think of this as a simple macro calculator: your estimated macros are based on your body weight, your calorie target and your goal, practical starting estimates, not exact dietary requirements.
Protein starts from a body-weight-based estimate and changes with your goal: 1.6 g per kg when losing weight or building muscle (1.0–1.1 g per pound), 1.4 g per kg for maintenance and weight gain. People in a deficit should aim toward the higher end to maximise muscle preservation while losing fat.
Fat is estimated at approximately 30% of your calorie target. Carbohydrates make up the remaining calories, the grams come from the standard energy factors: protein 4 kcal/g, carbohydrate 4 kcal/g, fat 9 kcal/g.
Worked example, the 2,246 kcal maintenance of the 62 kg woman above, switching the goal to lose: target 1,909 kcal, protein 1.6 × 62 = 99 g, fat = 30% × 1,909 ÷ 9 = 64 g, carbs = (1,909 − 99×4 − 64×9) ÷ 4 = 234 g. You do not need to hit these exactly every day, within ±10% is close enough; weekly consistency is what matters.
A calorie calculator estimates energy needs; it does not directly measure your metabolism. Predictive equations give a useful starting point, but real needs vary with muscle mass, genetics, health conditions, how active you really are, and even food-label error.
The honest check is the scale and the mirror: eat your target consistently for two to three weeks and see what your weight does. Losing faster than planned? Eat a little more. Not losing? Trim 100–200 kcal or move more. Adjust until reality matches the plan.
One formula comparison worth knowing: Katch-McArdle bases BMR on lean body mass instead of total weight, so it can be more accurate if you know your body fat percentage. Mifflin-St Jeor uses only weight, height, age and sex, and is the one most major tools use because it needs no body fat figure.
This calculator is designed for adults aged 18 and over. It is not intended for pregnancy or breastfeeding, and anyone with a medical condition affecting energy needs should get individual guidance.
Two diets with the same calorie count can affect you very differently. Protein and fiber keep you full longer and protect muscle in a deficit, so whole foods, lean meat, fish, eggs, beans, vegetables, whole grains, make a calorie target far easier to hit than the same calories from processed snacks. Portion size is the other lever: larger servings raise intake even when the food is healthy.
For weight loss, also mind the extras that never reach the calculator: sauces, cooking oils and drinks can quietly add hundreds of calories a day. For muscle gain, carbs matter for training performance, dropping them too low impairs workout quality and slows progress, and protein needs resistance training to turn into muscle.
Finally, if tracking every gram feels heavy, you are not alone: some people do well with zigzag calorie cycling, alternating higher and lower calorie days while keeping the weekly average at target. The idea is flexibility and avoiding plateaus, though the total deficit over the week is what drives weight loss.
Your needs depend on age, sex, height, weight and activity. As rough guides, the US Dietary Guidelines put most adult women at about 1,600–2,400 kcal a day and most adult men at 2,200–3,000. Enter your details in the calculator above for your personal maintenance number, deficit and surplus.
Maintenance calories are your Total Daily Energy Expenditure (TDEE): your BMR multiplied by an activity factor. BMR comes from the Mifflin-St Jeor equation; then multiply by 1.2 (sedentary) up to 1.9 (extra active). That TDEE is the calorie level that keeps your weight stable.
BMR estimates the energy you burn at rest; TDEE adjusts that estimate for activity and represents your total daily energy expenditure. TDEE is the estimate used as the starting point for your daily calorie target, BMR alone would starve every bit of activity.
A calorie deficit occurs when you consume less energy than your body uses. Sustaining an energy deficit over time leads to weight loss, although individual results vary. A deficit of about 500 kcal a day works out to roughly 0.5 kg (1 lb) of fat loss per week.
A deficit of about 250–500 kcal a day below maintenance is the usual safe range, giving roughly 0.5–1 lb of fat loss per week. Larger cuts speed the loss but raise the risk of muscle loss, fatigue and rebound eating.
Zigzag calorie cycling alternates higher and lower calorie days while keeping the weekly average at your target. The idea is to add flexibility and avoid a plateau. The total deficit over the week is what drives weight loss.
Mifflin-St Jeor estimates BMR from weight, height, age and sex, it needs no body fat figure. Katch-McArdle bases BMR on lean body mass instead, so it can be more accurate if you know your body fat percentage. Most tools use Mifflin-St Jeor for simplicity.
No. It uses predictive equations and an estimated activity level, so the result is a useful starting estimate, not a direct measurement of your metabolism. Use it as the starting point, then adjust based on how your weight actually moves over two to three weeks.
Gain weight uses a larger surplus aimed at increasing overall body weight (muscle, fat, glycogen and water). Build muscle uses a smaller controlled surplus, about 10%, plus a higher protein estimate, and assumes regular resistance training, because extra calories alone do not become muscle.