Calorie Calculator: Daily Energy Needs

By HesaplayıcıUpdated: September 29, 2026

The calorie calculator estimates the energy your body uses in a day and the calories for your goal. Enter your sex, age, weight, height, activity level and goal. It finds your basal metabolic rate with the Mifflin–St Jeor equation, multiplies it by an activity factor and splits the calories into carbohydrate, protein and fat grams. It is not medical advice.

Worked example: A moderately active woman, 31 years, 65 kg, 168 cm

Daily calories for your goal

2,145 kcal/day

Basal metabolic rate (BMR): 1,384 kcal/day
Daily calorie need: 2,145 kcal/day
Daily energy need in kJ: 8,976 kJ/day
Daily energy for your goal in kJ: 8,976 kJ/day
Carbohydrate: 268 g/day
Protein: 107 g/day
Fat: 72 g/day

Step by step

Basal metabolic rate (BMR)
BMR = 10 × weight + 6.25 × height − 5 × age − 161
BMR = 10 × 65 + 6.25 × 168 − 5 × 31 − 161 = 1,384 kcal
Daily calorie need
daily energy need = BMR × activity factor
daily energy need = 1,384 × 1.55 = 2,145 kcal
Daily energy need in kJ
daily energy need (kJ) = BMR × activity factor × 4.184
daily energy need (kJ) = 1,384 × 1.55 × 4.184 = 8,976 kJ
Daily calories for your goal
goal calories = daily energy need
goal calories = 2,145 = 2,145 kcal
Daily energy for your goal in kJ
goal energy (kJ) = goal calories × 4.184
goal energy (kJ) = 2,145.2 × 4.184 = 8,976 kJ
Carbohydrate
carbohydrate = goal calories × carbohydrate share / 4
carbohydrate = 2,145 × 50% / 4 = 268 g
Protein
protein = goal calories × protein share / 4
protein = 2,145 × 20% / 4 = 107 g
Fat
fat = goal calories × fat share / 9
fat = 2,145 × 30% / 9 = 72 g

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How to use

Choose your Units: Metric (kg, cm), Pounds (lb; ft, in) or Stones (st, lb; ft, in).
Choose your Sex: Female or Male.
Enter your Age in years, then your Weight and your Height in the units you chose.
Choose the Activity level closest to your weekly exercise.
Choose your Goal: keep your weight, lose weight, lose weight faster or gain weight.
If you want, change the carbohydrate, protein and fat shares under More options. The three shares must add up to 100%.
Press Calculate.

Formula

BMR (men) = 10 × weight + 6.25 × height − 5 × age + 5
BMR (women) = 10 × weight + 6.25 × height − 5 × age − 161
Daily calorie need = BMR × activity factor
Goal calories (lose) = max(daily need − 500 or 750; lower bound)
Goal calories (gain) = daily need + 500
Energy (kJ) = calories (kcal) × 4.184
Carbohydrate or protein (g) = goal calories × share / 4
Fat (g) = goal calories × share / 9

BMR is the basal metabolic rate in kcal per day. Weight is in kilograms, height in centimetres and age in years. With pounds or stones, the calculator converts first: 1 lb = 0.45359237 kg, 14 lb to a stone, 1 in = 2.54 cm. The activity factors are the American Council on Exercise table: sedentary 1.2, lightly active 1.375, moderately active 1.55, very active 1.725, extremely active 1.9. To keep your weight, the goal calories are the daily need.

max is the larger of the two values. The lower bound of a loss goal is 1,200 kcal for women and 1,500 kcal for men, or the daily need when it is lower. These values are from the US adult obesity guideline (AHA/ACC/TOS 2013). No guideline sets a value for weight gain; the calculator adds the same 500 kcal. The grams use the Atwater factors (FAO 2003). The default shares are inside the adult ranges of the Turkish dietary guidelines (TÜBER 2022): carbohydrate 45–60%, protein 10–20%, fat 20–35%. Calories and grams are rounded to whole numbers. The calculator also gives the daily need and the goal in kilojoules (kJ): 1 kcal is 4.184 kJ (FAO 2003). The kJ value comes from the unrounded calories and is rounded to whole kJ.

Worked example

The worked example on this page shows a woman of 31 years, 65 kg and 168 cm who exercises 3–5 days a week and wants to keep her weight. The steps give the basal metabolic rate, the daily calorie need, the goal calories, these two values in kJ and the macros in grams with the default shares.

Limits

The equation comes from healthy adults and gives an estimate; a measured value can differ from person to person. Pregnancy, breastfeeding, illness, medicines and a high muscle share are not taken into account. The goal calories are a starting point; how fast your weight changes differs from person to person. The result is not medical advice; ask your doctor or a dietitian about a diet plan.

Frequently Asked Questions

What is the basal metabolic rate?

It is the energy your body uses in a day at rest, for its basic functions only. The calculator estimates it with the Mifflin–St Jeor equation.

Which activity level should I choose?

Sedentary if you have a desk job and no exercise; lightly active for exercise 1–3 days a week, moderately active for 3–5 days, very active for 6–7 days. Extremely active fits training twice a day or hard physical work.

Why the Mifflin–St Jeor equation?

It was developed in 1990 from the resting energy expenditure measured in 498 healthy adults. The same study found that the older Harris–Benedict equations overestimated the measured value by about 5%.

How many calories should I eat to lose weight?

The lose weight goal takes 500 kcal a day off your daily need, the faster goal 750 kcal. The result does not go below 1,200 kcal for women and 1,500 kcal for men, the lower bounds of the AHA/ACC/TOS 2013 guideline. Ask your doctor or a dietitian about a diet plan.

How are the macros in grams calculated?

The goal calories are split by the carbohydrate, protein and fat shares. A gram of carbohydrate or protein is 4 kcal, a gram of fat 9 kcal. The default shares are 50% carbohydrate, 20% protein and 30% fat, inside the adult ranges of the Turkish dietary guidelines (TÜBER 2022).

Calculation rules

The BMR uses the Mifflin–St Jeor equation (Mifflin et al., Am J Clin Nutr 1990): for men 10 × weight + 6.25 × height − 5 × age + 5, for women the same sum − 161.
The daily need is BMR × activity factor. The factors (1.2, 1.375, 1.55, 1.725, 1.9) are the American Council on Exercise (ACE) table.
The BMR and the daily need are rounded to whole kcal; the daily need uses the rounded BMR.
The kilojoule (kJ) values come from the unrounded kcal of the daily need and the goal and are rounded to whole kJ: 1 kcal = 4.184 kJ (FAO 2003). Thus they can differ by less than 3 kJ from the rounded kcal × 4.184.
A weight loss goal takes 500 or 750 kcal off the daily need, but not below 1,200 kcal for women and 1,500 kcal for men (or the daily need, when it is lower), as the US adult obesity guideline says (AHA/ACC/TOS 2013). The gain goal adds 500 kcal; no guideline sets a value for it.
The macronutrients come from the goal calories: a gram of carbohydrate or protein is 4 kcal, a gram of fat 9 kcal (Atwater factors). The default split is 50% carbohydrate, 20% protein, 30% fat, inside the adult ranges of the Turkish dietary guidelines (TÜBER 2022): carbohydrate 45–60%, protein 10–20%, fat 20–35%. The three shares must add up to 100%. Grams are rounded to whole numbers.
With pounds or stones, the weight and height are converted to kg and cm (1 lb = 0.45359237 kg, 1 in = 2.54 cm) before the equation.
The equation comes from healthy adults; pregnancy, breastfeeding, illness and athletic body composition are not taken into account. The result is an estimate, not medical advice.