Estimate your basal metabolic rate and the daily calories that maintain, lose or gain weight at your activity level.
Two acronyms come up whenever people talk about calories: BMR and TDEE. They’re related but very different numbers, and mixing them up leads to diets that are either too aggressive or don’t work at all.
BMR: basal metabolic rate
Your BMR is the energy your body burns at complete rest, lying still in a comfortable room after an overnight fast. It powers the essentials:
- breathing and circulation
- brain and nervous system activity
- cell growth and repair
- maintaining body temperature
For most adults, BMR is 60–70% of total daily calorie burn. It depends mainly on body size, lean mass, age and sex.
How BMR is estimated
The Mifflin–St Jeor equation (1990) is widely considered the most accurate everyday formula:
- Men:
10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5 - Women:
10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161
TDEE: total daily energy expenditure
Your TDEE is everything you burn in a day. It’s BMR plus:
| Component | Share of TDEE | What it is |
|---|---|---|
| BMR | ~60–70% | Staying alive at rest |
| NEAT | ~15–30% | Non-exercise activity: walking, fidgeting, chores, standing |
| Exercise | ~5–10% | Deliberate workouts |
| Thermic effect of food | ~10% | Energy used to digest food |
In practice, TDEE is estimated by multiplying BMR by an activity factor between 1.2 and 1.9. Choosing that factor honestly is the hardest part; see How to Choose Your Activity Level for Calorie Calculators (Honestly).
Worked example
Woman, 35 years, 165 cm, 68 kg, lightly active:
- BMR = 680 + 1,031.25 − 175 − 161 = 1,375 kcal
- TDEE = 1,375 × 1.375 = ≈ 1,891 kcal
So she burns about 1,375 kcal doing nothing at all, and roughly 1,890 kcal on a typical day. The calorie calculator shows both numbers instantly.
Which number should you eat?
Eat around your TDEE, not your BMR.
- To maintain weight: eat at TDEE.
- To lose weight: eat below TDEE, typically 250–550 kcal less.
- To gain weight: eat above TDEE.
Eating at or below BMR for long periods is usually too aggressive. It can lead to muscle loss, fatigue, nutrient shortfalls and a strong drop in NEAT as your body conserves energy. Most guidance suggests not going below about 1,200 kcal/day for women or 1,500 kcal/day for men without medical supervision. For sustainable targets, see How Many Calories Should I Eat to Lose Weight? A Realistic Guide.
What changes BMR and TDEE
- Muscle mass: muscle tissue burns more at rest than fat, so strength training nudges BMR up.
- Weight loss: a smaller body burns less, so TDEE falls as you lose weight. Recalculate every 4–5 kg.
- Age: BMR declines slowly, mainly through muscle loss.
- Daily movement: NEAT varies enormously between people, by up to several hundred calories a day.
- Sleep and stress: poor sleep tends to raise appetite and lower activity.
Accuracy
Mifflin–St Jeor predicts BMR within about 10% for most people, but individuals vary. Treat your TDEE as a starting estimate: eat at that level for two to three weeks, track your weight trend, and adjust by 100–200 kcal if needed.
Try your own numbers below.
Try it: Calorie Calculator
- Basal metabolic rate (BMR)
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- Mild weight loss (−0.25 kg/wk)
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- Weight loss (−0.5 kg/wk)
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- Mild weight gain (+0.25 kg/wk)
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- Weight gain (+0.5 kg/wk)
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Estimate your basal metabolic rate and the daily calories that maintain, lose or gain weight at your activity level.