How Many Calories Do You Need? BMR, TDEE and Weight Goals

Your body burns energy all day, even when you rest. Knowing roughly how much helps you plan how much to eat, whether you want to stay the same, lose weight or gain it.

BMR and TDEE

• Basal metabolic rate (BMR) is the energy your body needs at complete rest to keep you alive: breathing, circulation and keeping warm.
• Total daily energy expenditure (TDEE) is BMR plus everything you do, from walking to training.

A widely used estimate of BMR is the Mifflin-St Jeor equation, which uses weight, height, age and sex. TDEE is then BMR multiplied by an activity factor: about 1.2 for little exercise, 1.375 for light exercise, 1.55 for moderate, 1.725 for hard and 1.9 for very hard exercise or a physical job. The Calorie Calculator does this in metric or imperial units.

Changing your weight

A common rule of thumb says about 3,500 calories equal a pound of body weight, so a daily gap of 500 calories is roughly a pound a week. The body adapts, so real results vary and slow down over time. Very low targets, below roughly 1,200 calories for women or 1,500 for men, should only be followed with medical supervision, and the calculator flags them.

Where BMI fits

Body mass index compares weight with height and is a rough screening number, not a measure of health. The BMI Calculator shows it, and the guide on BMI explains what it misses.

Limits of any calculator

• Estimates can be off by 10 percent or more for an individual.
• Muscle, age, medical conditions and medicines change energy needs.
• Pregnancy, growing children and some conditions need different advice.
• Use the result as a starting point, watch what happens over a few weeks, and talk to a doctor or dietitian before big changes.