acalculator

How many calories do I need a day?

Enter your sex, age, height, weight and activity level to see the calories a day that keep your weight steady, and the targets to lose or gain weight.

Your numbers

Units
Sex
Multiplies your BMR by 1.2, 1.375, 1.55, 1.725 or 1.9.
More options
BMR formula
Calories to keep your weight
1,927

You need about 1,927 calories a day to keep your current weight.

Lose 0.5 lb (0.23 kg) a week
1,677
Lose 1 lb (0.45 kg) a week
1,427
Gain 0.5 lb (0.23 kg) a week
2,177
Gain 1 lb (0.45 kg) a week
2,427
BMR (calories at complete rest)
1,401
Note
Losing 2 lb a week would mean eating under 1,200 calories a day, below the lowest diet the weight-loss guideline suggests.

Calories to keep your weight: 1,927. You need about 1,927 calories a day to keep your current weight.

Calories to keep your weight by age

This calculator gives general information only. It is not medical advice and does not replace a doctor or other health care provider. Talk with a professional about your results. Terms of use

How to calculate

Estimates the calories a day an adult needs to keep their weight (BMR × activity factor), and the daily targets to lose or gain 0.5 to 2 pounds a week.

Example with the default inputs (Sex Female, Age 30, Height 5 ft 5 in, Weight 150 lb, Activity Light: exercise 1 to 3 days, BMR formula Mifflin-St Jeor): You need about 1,927 calories a day to keep your current weight.

Method: Calories to keep your weight = BMR × activity factor, with BMR from Mifflin-St Jeor (10 × kg + 6.25 × cm − 5 × age + 5, or − 161 for women) or the revised Harris-Benedict; each 500 calories a day less loses about 1 lb a week.

  • The formulas are for adults (Mifflin-St Jeor was fitted on people aged 19 to 78). They are not for children, pregnancy or breastfeeding.
  • Activity factors: sedentary 1.2, light 1.375, moderate 1.55, very active 1.725, extra active 1.9.
  • A pound of body weight is taken as 3,500 calories, so 500 fewer calories a day is about 1 lb a week. Real loss slows over time as your needs fall.
  • Loss targets under 1,200 calories a day (women) or 1,500 (men) are left out, the low end of the diets in the 2013 AHA/ACC/TOS guideline.
  • This is an estimate for planning, not medical advice.

Machine-readable copies: Markdown, JSON.

Worked examples

Each example is checked against the calculator on every build.

  1. Sex Female, Age 30, Height 5 ft 5 in, Weight 150 lb, Activity Light: exercise 1 to 3 days, BMR formula Mifflin-St Jeor gives BMR (calories at complete rest) 1,401.263555, Calories to keep your weight 1,926.737388, Lose 0.5 lb (0.23 kg) a week 1,676.737388, Lose 1 lb (0.45 kg) a week 1,426.737388, Gain 1 lb (0.45 kg) a week 2,426.737388, Note Losing 2 lb a week would mean eating under 1,200 calories a day, below the lowest diet the weight-loss guideline suggests..Source: Mifflin et al. 1990 and the 1.375 activity factor; hand calculation in content.mdx
  2. Sex Male, Age 35, Height 5 ft 10 in, Weight 180 lb, Activity Moderate: exercise 3 to 5 days, BMR formula Mifflin-St Jeor gives BMR (calories at complete rest) 1,757.716266, Calories to keep your weight 2,724.460212, Lose 2 lb (0.91 kg) a week 1,724.460212, Gain 0.5 lb (0.23 kg) a week 2,974.460212.Source: Mifflin et al. 1990 and the 1.55 activity factor; hand calculation in content.mdx
  3. Sex Female, Age 40, Height 5 ft 5 in, Weight 132.3 lb, Activity Sedentary: little or no exercise, BMR formula Harris-Benedict gives BMR (calories at complete rest) 1,340.383, Calories to keep your weight 1,608.4596.Source: Roza and Shizgal 1984 (revised Harris-Benedict) and the 1.2 activity factor; hand calculation in content.mdx
  4. Sex Female, Age 60, Height 5 ft 1 in, Weight 110.2 lb, Activity Sedentary: little or no exercise, BMR formula Mifflin-St Jeor gives Calories to keep your weight 1,209.3, Note Losing 0.5 lb, 1 lb or 2 lb a week would mean eating under 1,200 calories a day, below the lowest diet the weight-loss guideline suggests..Source: Mifflin et al. 1990; AHA/ACC/TOS 2013 guideline (1,200 kcal a day for women); hand calculation in content.mdx

How it works

Step 1: basal metabolic rate (BMR). BMR is the calories a day your body uses at complete rest. Weight is in kilograms, height in centimetres and age in whole years.

Mifflin-St Jeor (1990), the default:

  • Men: BMR = 10 × weight + 6.25 × height − 5 × age + 5
  • Women: BMR = 10 × weight + 6.25 × height − 5 × age − 161

Revised Harris-Benedict (Roza and Shizgal, 1984), under "More options":

  • Men: BMR = 88.362 + 13.397 × weight + 4.799 × height − 5.677 × age
  • Women: BMR = 447.593 + 9.247 × weight + 3.098 × height − 4.330 × age

Step 2: calories to keep your weight. Calories to keep your weight = BMR × activity factor.

  • Sedentary (little or no exercise): × 1.2
  • Light (exercise 1 to 3 days a week): × 1.375
  • Moderate (exercise 3 to 5 days a week): × 1.55
  • Very active (hard exercise 6 to 7 days a week): × 1.725
  • Extra active (hard daily exercise and physical work): × 1.9

The factor is the physical activity level (PAL): total daily energy expenditure divided by BMR (FAO/WHO/UNU). These five values are the multipliers most often used with the equations above. FAO/WHO/UNU puts most adults' lifestyles between PAL 1.40 and 2.40, so the lower factors are cautious for people who move about during the day.

Step 3: targets to lose or gain. One pound of body weight is taken as 3,500 calories (Wishnofsky, 1958), so a change of 500 calories a day is 3,500 calories a week, about 1 pound.

  • Lose 0.5 lb (0.23 kg) a week: keep your weight − 250
  • Lose 1 lb (0.45 kg) a week: keep your weight − 500
  • Lose 2 lb (0.91 kg) a week: keep your weight − 1,000
  • Gain 0.5 lb (0.23 kg) a week: keep your weight + 250
  • Gain 1 lb (0.45 kg) a week: keep your weight + 500

A loss target is left out when it is below 1,200 calories a day for women or 1,500 for men, the low end of the weight-loss diets in the 2013 AHA/ACC/TOS guideline. A note then names the targets left out. A target exactly at the limit is shown.

The chart shows the calories to keep your weight at ages 18 to 80, with everything else as you entered it.

Assumptions

  • The formulas are for adults. Mifflin-St Jeor was fitted on healthy people aged 19 to 78. They do not apply to children, or during pregnancy or breastfeeding.
  • The 3,500-calorie rule is a simplification. Your needs fall as you lose weight, so real loss is slower than the rule predicts over months (Hall and others, 2011).
  • Nothing is rounded until the result is shown.
  • This calculator gives an estimate for planning. It is not medical advice. Talk to a doctor or a registered dietitian before a large change in diet, and if you are pregnant, breastfeeding, under 18, or have a health condition.

Worked examples by hand

A 30-year-old woman, 5 ft 5 in, 150 lb, lightly active. 150 lb = 150 × 0.45359237 = 68.039 kg and 5 ft 5 in = 65 in = 165.1 cm. BMR = 10 × 68.039 + 6.25 × 165.1 − 5 × 30 − 161 = 680.39 + 1,031.88 − 150 − 161 = 1,401.26. To keep her weight: 1,401.26 × 1.375 = 1,926.74 calories a day. To lose 0.5 lb a week: 1,676.74; 1 lb a week: 1,426.74. To lose 2 lb a week she would need 926.74, which is under 1,200, so that target is left out. To gain 1 lb a week: 2,426.74.

A 35-year-old man, 5 ft 10 in, 180 lb, moderately active. 180 lb = 81.647 kg and 70 in = 177.8 cm. BMR = 816.47 + 1,111.25 − 175 + 5 = 1,757.72. To keep his weight: 1,757.72 × 1.55 = 2,724.46. To lose 2 lb a week: 2,724.46 − 1,000 = 1,724.46, which is above 1,500, so it is shown. To gain 0.5 lb a week: 2,974.46.

Harris-Benedict: a 40-year-old woman, 165 cm, 60 kg, sedentary. BMR = 447.593 + 9.247 × 60 + 3.098 × 165 − 4.330 × 40 = 447.593 + 554.82 + 511.17 − 173.2 = 1,340.38. To keep her weight: 1,340.38 × 1.2 = 1,608.46.

A 60-year-old woman, 155 cm, 50 kg, sedentary. BMR = 500 + 968.75 − 300 − 161 = 1,007.75. To keep her weight: 1,007.75 × 1.2 = 1,209.3. Even the 0.5 lb target (959.3) is under 1,200, so no loss target is shown.

Other questions people ask

How many calories do I need a day?

It depends on your size, age, sex and activity. This calculator first estimates your basal metabolic rate (BMR), the calories your body uses at rest, then multiplies it by an activity factor from 1.2 (sedentary) to 1.9 (extra active). For example, a 30-year-old woman who is 5 ft 5 in, weighs 150 lb and exercises 1 to 3 days a week needs about 1,927 calories a day to keep her weight.

How many calories should I eat to lose weight?

A common rule is that a pound of body weight holds about 3,500 calories, so eating 500 fewer calories a day than you burn loses about 1 pound a week. The calculator shows targets for 0.5, 1 and 2 pounds a week. The CDC notes that people who lose about 1 to 2 pounds a week are more likely to keep the weight off.

Why are some weight-loss targets missing?

The 2013 guideline from the American Heart Association, the American College of Cardiology and The Obesity Society suggests weight-loss diets of 1,200 to 1,500 calories a day for women and 1,500 to 1,800 for men. When a target would fall under 1,200 (women) or 1,500 (men) calories a day, the calculator leaves it out and says so. Eating less than that should be done only with a health professional.

Which BMR formula should I choose?

Mifflin-St Jeor is the default. A 2005 systematic review found it predicted resting metabolic rate within 10% of the measured value in more healthy adults than the other equations it tested. The revised Harris-Benedict equation (1984) is also offered for comparison. It usually gives a higher BMR, by up to about 350 calories a day for heavy people.

How accurate is this estimate?

It is a starting point. Equations based on height, weight, age and sex can be off by 10% or more for a given person, and the activity factor is a broad guess. Track your weight for a few weeks: if it moves when you want it steady, adjust your calories by 100 to 200 a day.

Does my calorie need change as I lose weight?

Yes. A lighter body burns fewer calories, so the same intake gives a smaller deficit over time and weight loss slows. Enter your new weight every few weeks. The weight loss calculator shows how this slowing plays out over months.