How Many Calories Do You Need? BMR and TDEE Explained With Examples
"How many calories should I eat?" is one of the most searched health questions, and the honest answer is "it depends". It depends on your body, how active you are and what you want to achieve. The good news is that you can get a sensible estimate in a couple of minutes. This guide explains the two numbers behind it, BMR and TDEE, with worked examples. You can calculate yours in the TDEE calculator.
BMR: what your body burns at rest
Your basal metabolic rate (BMR) is the energy your body uses to keep you alive while doing nothing: breathing, circulating blood, regulating temperature, running your organs. For most people it accounts for about 60% to 70% of the calories they burn in a day.
A widely used estimate is the Mifflin-St Jeor equation:
- Men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5
- Women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161
TDEE: your total daily burn
Your total daily energy expenditure (TDEE) adds the energy you use moving, exercising and digesting food. It is simply BMR multiplied by an activity factor:
| Activity level | Description | Multiplier |
|---|---|---|
| Sedentary | Desk job, little exercise | 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 |
| Extra active | Physical job plus training | 1.9 |
If you eat about your TDEE, your weight tends to stay stable. Eat less and you tend to lose, more and you tend to gain.
Worked example 1: a woman, 35, 165 cm, 70 kg, light exercise
BMR = 10 × 70 + 6.25 × 165 − 5 × 35 − 161 = 700 + 1,031.25 − 175 − 161 = 1,395 kcal
TDEE = 1,395 × 1.375 ≈ 1,918 kcal a day.
Worked example 2: a man, 30, 180 cm, 80 kg, moderately active
BMR = 10 × 80 + 6.25 × 180 − 5 × 30 + 5 = 800 + 1,125 − 150 + 5 = 1,780 kcal
TDEE = 1,780 × 1.55 ≈ 2,759 kcal a day.
Using TDEE to set a goal
To maintain weight: eat around your TDEE.
To lose weight: eat below it. A commonly used rule of thumb is that about 3,500 kcal corresponds to roughly one pound (0.45 kg) of body weight, so a daily deficit of about 500 kcal leads to a loss of about one pound a week. Real results vary, because the body adapts and water weight fluctuates.
To gain weight: eat above it, with a modest surplus of around 250 to 500 kcal.
For the woman in example 1, a 500 kcal deficit gives about 1,418 kcal a day. That is low, and it shows why a smaller deficit is often wiser. Very low intakes are hard to sustain, can leave you short of nutrients and, for many people, are not appropriate without professional supervision. A gradual loss of roughly 0.25 to 0.5 kg (0.5 to 1 lb) a week is a commonly recommended pace.
Why the estimate can be off
These formulas predict an average person, and individuals differ.
- Muscle mass: muscle burns more than fat, so two people of the same weight can have different BMR.
- Activity level: it is easy to overestimate. Be honest about how many days you really train.
- Genetics, hormones and medical conditions all matter.
- Adaptation: as you lose weight, your TDEE falls, so the same intake produces less deficit over time.
Treat the number as a starting point. Track your weight over two to three weeks. If it is not moving the way you want, adjust your intake by 100 to 200 kcal and watch again.
Calories are not everything
Two diets with the same calories can feel very different. Protein helps you stay full and preserve muscle. Fibre, found in vegetables, fruit, legumes and whole grains, helps with fullness too. Sleep, stress and strength training influence how your body uses energy. Calorie counting is a tool, not a verdict on how healthy a diet is.
A simple way to put it into practice
- Calculate your TDEE with the formula above or a calculator.
- Choose a goal: maintain, a gentle deficit or a modest surplus.
- Weigh yourself at the same time of day, a few times a week, and look at the weekly average.
- After two to three weeks, adjust.
- Focus on foods that keep you full and energized, not only on the number.
Who should not rely on a calculator
Calorie estimates are not suitable for children and teenagers, people who are pregnant or breastfeeding, people with a history of eating disorders, or anyone with a medical condition that affects metabolism or nutrition. In these cases, talk to a doctor or a registered dietitian.
This article is general information and not medical advice. Speak to a qualified professional before making significant changes to your diet or exercise.