Nutrients Calculator
Enter your age, sex, weight, height, activity level and weight goal and this calculator estimates your daily calorie needs with the Mifflin-St Jeor equation, adjusts those calories for your goal, splits them into protein, fat and carbohydrate grams, and suggests a daily water intake of about 1 mL per calorie. It does not track vitamins or minerals, and those limits are stated up front rather than hidden in the fine print.
Nutrients Calculator
Daily calories, macro grams and water from the Mifflin-St Jeor equation
Goal-adjusted estimate from the Mifflin-St Jeor equation: Lose subtracts 500 kcal, Maintain keeps maintenance calories, Gain adds 300 kcal, each with its own macro split, plus a water guideline of roughly 1 mL per kcal. It is a planning number, not a medical prescription.
Quick Answer
For a 30-year-old man weighing 70 kg at 175 cm who is moderately active, this calculator estimates 2,556 kcal/day, split into 127.8 g protein, 85.2 g fat and 319.4 g carbohydrates, plus about 2,556 mL of water. The calories come from the Mifflin-St Jeor equation multiplied by an activity factor of 1.55; on Maintain the macros come from a 20% / 30% / 50% split, which sits inside the accepted AMDR ranges. Pick Lose or Gain and the calorie target and split change with the goal, as the formula section shows.
Key takeaways
- Calories are estimated with Mifflin-St Jeor, the most widely validated BMR equation, then scaled by your activity level (TDEE).
- Macros use a goal-specific split: Lose 30% protein / 30% fat / 40% carbohydrates on 500 kcal below maintenance, Maintain 20% / 30% / 50% at maintenance, Gain 20% / 30% / 50% on 300 kcal above maintenance.
- The tool does not track vitamins, minerals, fiber or meal logging. A companion micronutrient calculator exists for that.
- Water guidance is about 1 mL per kcal, a planning rule from the Food and Nutrition Board, not a medical prescription.
How to use this calculator
Six inputs, one click. Enter your age in years, select your sex, and enter your weight in kilograms and height in centimeters. Pick the activity level that best matches a normal week, including both exercise and physical work, pick your weight goal, then click Calculate nutrients. The results box shows your goal line first, then five numbers: daily calories, protein, fat, carbohydrate grams, and a water guideline in milliliters. Use Reset any time to return to the example values.
The example values are not random. They describe a 30-year-old man, 70 kg, 175 cm, moderately active, and the article's worked example below runs those exact numbers through the formula so you can check the tool yourself. If you think in pounds and inches, divide pounds by 2.205 to get kilograms and multiply inches by 2.54 to get centimeters before entering them.
The formula behind the numbers
Every output traces back to four steps: estimate resting burn, scale it to a full day, adjust for your goal, then divide the calories into macros and water.
Basal metabolic rate: Mifflin-St Jeor
The calculator uses the Mifflin-St Jeor equation, published in 1990 and repeatedly found the most accurate of the common BMR formulas for healthy adults in validation studies:
Men: BMR = 10 x weight(kg) + 6.25 x height(cm) - 5 x age + 5
Women: BMR = 10 x weight(kg) + 6.25 x height(cm) - 5 x age - 161
BMR is what your body burns at complete rest. It is not your daily need; nobody spends 24 hours at rest.
Total daily energy expenditure: activity factors
TDEE = BMR x activity factor. The calculator uses the classic five-step scale, the same multipliers found in the National Academies' DRI reports:
| Activity level | Meaning | Factor |
|---|---|---|
| Sedentary | Little or no exercise, desk work | x 1.2 |
| Lightly active | Light exercise or sports 1-3 days/week | x 1.375 |
| Moderately active | Moderate exercise or sports 3-5 days/week | x 1.55 |
| Active | Hard exercise or sports 6-7 days/week | x 1.725 |
| Very active | Very hard training, twice-a-day sessions, or a physical job | x 1.9 |
Macro split and water
Goal adjustment comes first: Lose subtracts 500 kcal from TDEE (never below BMR, where the target floors), Maintain keeps TDEE, Gain adds 300 kcal. Then protein grams = target calories x protein share / 4, fat grams = target calories x fat share / 9, carbohydrate grams = target calories x carbohydrate share / 4, water (mL) = target calories. The splits are Lose 30% / 30% / 40%, Maintain 20% / 30% / 50%, Gain 20% / 30% / 50%; Maintain and Gain sit inside the acceptable macronutrient distribution ranges (AMDR) set by the Institute of Medicine: protein 10-35%, fat 20-35%, carbohydrates 45-65%. Lose carbohydrates (40%) sit below the AMDR carbohydrate floor by design for a deficit split: the Lose split is a planning choice, not an AMDR-compliant one. The water rule, roughly 1 mL of water per kcal of energy need, comes from the Food and Nutrition Board’s water DRI.
Worked example, step by step
The example below uses the calculator's default inputs: 30-year-old man, 70 kg, 175 cm, moderately active. Run it yourself and you will get the same numbers.
1. Enter stats
Age 30, male, 70 kg, 175 cm, moderate activity
2. BMR
700 + 1,093.75 - 150 + 5 = 1,648.75 kcal
3. TDEE calories
1,648.75 x 1.55 = 2,555.6 → 2,556 kcal
4. Macros + water
127.8 g protein, 85.2 g fat, 319.4 g carbs, 2,556 mL water
The macro bars below show the worked-example grams side by side, scaled to the largest value:
And the same grams as shares of the 2,556 kcal: protein 511 kcal (20%), fat 767 kcal (30%), carbohydrates 1,278 kcal (50%). The three add back to 2,556, which is the check that the split is internally consistent. On Lose the same person gets 2,056 kcal (154.2 g protein, 68.5 g fat, 205.6 g carbs); on Gain, 2,856 kcal (142.8 g protein, 95.2 g fat, 356.9 g carbs).
What competing calculators miss or get wrong
Most macro tools on the ranking pages do four things this page deliberately handles differently:
- Goal math, shown in the open. Rival tools from ajdesigner, neftcal and health2planet quietly apply cut (x0.80), maintain (x1.00) or bulk (x1.10) multipliers to your calories. That is useful, but the adjustment is baked into their headline numbers. This tool states its goal adjustment on the results line itself (maintenance calories, minus 500, or plus 300), so a cut or bulk is a decision you see rather than a preset you never noticed.
- Protein treated as a percentage only. Percentage splits hide what matters: grams per kilogram of body weight. The protein badge under this tool's results converts your number to g/kg and checks it against the 1.6-2.2 g/kg range the sports-nutrition literature uses for active people, which no rival tool on the first page of results shows.
- No water guidance. The calculators reviewed show macros and stop. The 1 mL-per-kcal water rule is a genuine extra output with a real DRI behind it, not decoration.
- Feigned personalization. Several rival pages advertise “diet ratios,” “label checkers” and meal planners around a tool that is still just BMR x 1.55. The old version of this very page claimed goal modes it never had. This rebuild adds them for real: six inputs, a goal line, five outputs, every formula printed on the page. Meal logging is still not here, and still not claimed.
A note on the protein shares
At 127.8 g for a 70 kg man, the default Maintain result is 1.83 g/kg, inside the 1.6-2.2 g/kg the International Society of Sports Nutrition recommends for people training hard. Lose raises the protein share to 30% (154.2 g, 2.20 g/kg for the default man) precisely because a deficit is when muscle preservation matters most. If you are lifting, treat the badge reading as a flag, not a verdict: keep the calorie number, then raise protein toward 1.6-2.2 g/kg and take the calories from carbs or fat. If you want that workflow automated, a general macro calculator lets you set your own calorie target and split instead of taking this tool’s goal splits.
What this tool does not do
Honest limits, in one place. It does not estimate vitamins, minerals, fiber or any micronutrient; our micronutrient calculator exists for that. It now has Lose, Maintain and Gain modes, but those are simple planning targets (minus 500, as-is, plus 300 kcal), not a full diet program, so if your goal is a structured surplus plan, our bulking calories calculator sets the calorie target first. It does not log meals or read food labels. And like every BMR equation, it estimates: validation studies put Mifflin-St Jeor within about 10% for most healthy adults, which is good enough for planning and not precise enough for a clinical prescription.
Frequently asked questions
It estimates your daily calorie need from your age, sex, weight, height and activity level using the Mifflin-St Jeor equation, adjusts it for your weight goal (Lose minus 500 kcal, Maintain as-is, Gain plus 300 kcal), converts the target into protein, fat and carbohydrate grams with a goal-specific split, and suggests a water intake of about 1 mL per kcal. It does not estimate vitamins, minerals or fiber, and it does not log meals.
Validation studies have repeatedly found it the most accurate of the common BMR equations for healthy adults, typically landing within about 10% of measured resting metabolic rate. That is solid for planning meals and training, but it is an estimate, not a lab measurement, and it is less reliable for people with unusual body composition, since it uses total weight rather than lean mass.
Pick Lose, Maintain or Gain above the Calculate button. Lose subtracts 500 kcal from your maintenance calories (TDEE) and uses a 30% protein / 30% fat / 40% carbohydrate split, with the target floored at your BMR so a deficit never goes below resting burn. Maintain keeps TDEE with a 20% / 30% / 50% split. Gain adds 300 kcal to TDEE with a 20% / 30% / 50% split. The results line states the adjustment every time, and the macro grams are recalculated against the new target.
The tool uses a goal-specific split: Maintain 20% protein / 30% fat / 50% carbohydrates, Lose 30% / 30% / 40%, Gain 20% / 30% / 50%; Maintain and Gain sit inside the official acceptable ranges (protein 10-35%, fat 20-35%, carbs 45-65%), while Lose carbohydrates (40%) sit below the AMDR carbohydrate floor by design for a deficit split: the Lose split is a planning choice, not an AMDR-compliant one. Lose raises protein because a deficit is when muscle preservation matters most. The protein badge under the results converts your grams to g/kg and checks them against the 1.6-2.2 g/kg range used for active people, so you can see immediately whether the default suits your training.
No. It estimates energy and the three calorie-yielding macronutrients plus water. Micronutrient needs depend on your actual foods, not your body stats, so a body-stats tool cannot estimate them honestly. Track what you eat against the daily values if vitamins and minerals are your question.
It is about 1 mL of total water per kcal of estimated need, a planning rule from the Food and Nutrition Board. Total water includes water in food as well as drinks, and real needs rise with heat, exercise and illness. Treat it as a baseline for planning, not a medical prescription.
Pick the level that matches a normal week, counting both exercise and physical work. Most desk workers who train 3-5 days a week are "moderately active." When in doubt, pick the lower level: people consistently overestimate their activity, and an overstated factor inflates the calorie number more than any other input.
The tool takes metric inputs only: kilograms and centimeters. Divide pounds by 2.205 to get kilograms, and multiply inches by 2.54 to get centimeters. Entering imperial numbers as if they were metric will produce a wrong result, since the equation's constants assume kg and cm.
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References
- Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. A new predictive equation for resting energy expenditure in healthy individuals, The American Journal of Clinical Nutrition. Accessed October 23, 2026.
- Frankenfield DC, Roth-Yousey L, Compher C. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review, The American Journal of Clinical Nutrition. Accessed October 23, 2026.
- Institute of Medicine, National Academies. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. Accessed October 23, 2026.
- Institute of Medicine, National Academies. Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate. Accessed October 23, 2026.
- U.S. Department of Agriculture and U.S. Department of Health and Human Services. Dietary Guidelines for Americans, 2020-2025. Accessed October 23, 2026.
- Jäger R, Kerksick CM, Campbell BI, Cribb PJ, Wells SD, Skwiat TM, et al. International Society of Sports Nutrition position stand: protein and exercise, Journal of the International Society of Sports Nutrition. Accessed October 23, 2026.
- Harvard T.H. Chan School of Public Health. Types of Fat, The Nutrition Source. Accessed October 23, 2026.
- Harvard T.H. Chan School of Public Health. Carbohydrates and Blood Sugar, The Nutrition Source. Accessed October 23, 2026.
- U.S. National Library of Medicine. Protein in diet, MedlinePlus. Accessed October 23, 2026.
- American Heart Association. Dietary Fats. Accessed October 23, 2026.