Calorie / BMR Calculator

How Calorie / BMR Calculator Works

Your Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest just to keep you alive -- breathing, circulation, cell repair, and so on. This calculator estimates your BMR and then scales it by your activity level to estimate your Total Daily Energy Expenditure (TDEE), the maintenance calories needed to keep your weight steady.

Formula & Method

This calculator uses the Mifflin-St Jeor equation: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) + 5 for men, or the same formula with −161 instead of +5 for women. BMR is then multiplied by an activity multiplier (1.2 for sedentary up to 1.9 for extra active) to get your maintenance calories (TDEE). The ±500 cal/day figures for losing or gaining weight are simple estimates, since a sustained deficit or surplus of about 500 calories a day roughly corresponds to losing or gaining about 0.5 kg (1 lb) per week.

Worked Example

For a 30-year-old man, 170 cm tall, weighing 70 kg, at a "moderately active" activity level (multiplier 1.55): BMR = 10 × 70 + 6.25 × 170 − 5 × 30 + 5 = 700 + 1,062.5 − 150 + 5 = 1,617.5 cal/day. Maintenance calories (TDEE) = 1,617.5 × 1.55 ≈ 2,507 cal/day, with roughly 2,007 cal/day suggested to lose weight and roughly 3,007 cal/day to gain weight.

Frequently Asked Questions

Why is the BMR formula different for men and women?

The Mifflin-St Jeor equation uses a fixed offset of +5 for men and -161 for women to account for typical differences in body composition, such as average muscle mass, between the sexes at the same height and weight.

Which activity level should I choose?

Pick the option that best matches your typical week, not just workout days: Sedentary means little to no exercise, Lightly active is light exercise 1-3 days a week, Moderately active is moderate exercise 3-5 days a week, Very active is hard exercise 6-7 days a week, and Extra active covers very hard training or a physically demanding job on top of exercise.

Is the Mifflin-St Jeor equation the most accurate BMR formula?

It is one of the most widely used and is generally considered more accurate for most people than older formulas like Harris-Benedict, but any BMR equation is still an estimate -- actual metabolic rate varies with muscle mass, genetics, and health conditions that a height/weight/age formula can't capture.

Why 500 calories for losing or gaining weight?

One pound (about 0.45 kg) of body fat represents roughly 3,500 stored calories, so a daily deficit or surplus of about 500 calories works out to roughly one pound of weight change per week -- a commonly used, moderate pace for weight change.