How the calculation works
This calculator uses the Mifflin-St Jeor equation, published in 1990 and widely used by dietitians, to estimate your basal metabolic rate (BMR): the energy your body uses at rest just to keep you alive.
The equation takes your weight in kilograms, your height in centimetres and your age in years. Imperial values are converted first (1 lb = 0.4536 kg, 1 in = 2.54 cm).
The Mifflin-St Jeor formula
- Men:
BMR = 10 × weight + 6.25 × height − 5 × age + 5 - Women:
BMR = 10 × weight + 6.25 × height − 5 × age − 161 - Prefer not to say:
the average of both: BMR = 10 × weight + 6.25 × height − 5 × age − 78
Activity multipliers
Your BMR is then multiplied by an activity factor to give your total daily energy expenditure (TDEE), rounded to the nearest calorie.
| Activity level | Multiplier |
|---|---|
| Sedentary Little or no exercise, desk job | × 1.2 |
| Lightly active Light exercise 1 to 3 days a week | × 1.375 |
| Moderately active Moderate exercise 3 to 5 days a week | × 1.55 |
| Very active Hard exercise 6 to 7 days a week | × 1.725 |
Example: a 35-year-old woman who weighs 68 kg, is 168 cm tall and is lightly active has a BMR of 10 × 68 + 6.25 × 168 − 5 × 35 − 161 = 1,394 kcal. Her TDEE is 1,394 × 1.375 = 1,917 kcal a day.
What TDEE means
TDEE stands for total daily energy expenditure: everything you burn in a day. It includes your BMR, the energy it takes to digest food, everyday movement such as walking and standing, and deliberate exercise.
Eat roughly your TDEE and your weight should stay about the same. Eat less and you lose weight over time; eat more and you gain.
How to use your number
- Start with the figure for your goal and log what you eat for two to three weeks.
- Weigh yourself a few times a week at the same time of day and watch the trend, not single days.
- If your weight moves faster or slower than you want, adjust by 100 to 200 kcal and give it another two weeks.
- Recalculate after a big change in weight or activity.
Related calculators
- Macro calculator: split your daily calories into grams of protein, carbs and fat.
- Protein calculator: find a daily protein target from your body weight and goal.
Limitations
- It is an estimate. Metabolism differs from person to person, and the equation can be off by 10% or more for some people.
- It does not know your body composition. Very muscular people tend to burn more than predicted, and the estimate is less precise for people with obesity.
- It is not designed for people under 18, for pregnancy or breastfeeding, or for medical conditions that affect metabolism.
- Activity levels are broad categories, and most people overestimate how active they are. If you are unsure, pick the lower one.
