Calorie Calculator

Use age, sex, height, weight, and activity level to estimate resting energy needs and daily maintenance calories.

Estimated maintenance calories—kcal/day
Estimated resting energy (BMR)—kcal/day
How this estimate is calculated: This calculator uses the Mifflin–St Jeor equation to estimate basal metabolic rate (BMR), then multiplies that estimate by the selected activity factor to approximate total daily energy expenditure. Actual calorie needs can vary substantially from the estimate.
Important: This tool estimates maintenance energy needs for adults. It does not prescribe calorie restriction or weight-loss targets and is not intended for children, teens, pregnancy, or medical nutrition therapy.
For informational purposes only. Calorie needs vary with body composition, health, medications, pregnancy, training, metabolism, and other factors. This calculator is not medical or nutritional advice.

How to use the calorie calculator

Choose US units or Metric, then enter your age, sex, height, weight, and how active you usually are. Press Calculate calories to see two numbers:

  • Resting energy (BMR) – the calories your body uses at complete rest, just to keep you alive: breathing, circulation, and keeping warm.
  • Maintenance calories – an estimate of how many calories a day would keep your weight about the same at your activity level.

The formula behind it

This calculator uses the Mifflin–St Jeor equation, which is one of the most widely used formulas for estimating resting energy:

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

Your BMR is then multiplied by an activity factor:

  • Sedentary (little or no exercise): × 1.2
  • Lightly active (light exercise 1–3 days a week): × 1.375
  • Moderately active (moderate exercise 3–5 days a week): × 1.55
  • Very active (hard exercise 6–7 days a week): × 1.725
  • Extra active (very hard exercise or a physical job): × 1.9

Example: a 40-year-old man who is 5 feet 10 inches tall, weighs 180 pounds, and exercises moderately has a BMR of about 1,733 calories. Multiplied by 1.55, his maintenance estimate is about 2,686 calories a day.

Choosing the right activity level

Most people overestimate how active they are. A desk job with a 30-minute walk most days is usually “lightly active,” not “moderately active.” If you’re unsure, pick the lower level, track your weight for two or three weeks, and adjust.

How to use your result

Think of the number as a starting estimate, not a precise measurement. Real calorie needs vary from person to person by a few hundred calories a day because of muscle mass, genetics, sleep, and daily movement that isn’t formal exercise, like walking around the house or fidgeting.

The best way to fine-tune it is to watch what happens over time. If your weight stays steady while eating around your maintenance number, the estimate is about right for you.

If you are pregnant, breastfeeding, under 18, managing a medical condition, or planning a big change in your diet, talk to a doctor or registered dietitian. They can give advice that fits your situation.

Common questions

Why does the calculator ask for sex?

On average, men and women of the same size have different amounts of muscle and fat, which changes resting energy use. The equation uses a different constant for each.

Why do I need fewer calories as I get older?

Resting energy use tends to fall with age, partly because people often lose muscle. That’s why the formula subtracts 5 calories for every year of age.

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