BMR Calculator — Your Basal Metabolic Rate
Your basal metabolic rate is what your body would burn in a day if you did nothing at all — no walking, no work, no training. Breathing, circulation, keeping your organs running and your temperature steady all cost energy, and for most people that is the largest single share of daily calorie use.
It is not a target to eat to. It is the floor everything else is built on.
This is an estimate for healthy adults, not medical advice. If you are pregnant, breastfeeding, or managing a medical condition, speak to your doctor before acting on it.
How it works
We use the Mifflin-St Jeor equation, published in 1990 and still the closest fit for most modern adults. It takes weight, height, age and sex. Older calculators use Harris-Benedict, which tends to run high.
men: (10 x kg) + (6.25 x cm) - (5 x age) + 5 women: (10 x kg) + (6.25 x cm) - (5 x age) - 161
A worked example
A 28-year-old man, 175 cm and 72 kg: (10 x 72) + (6.25 x 175) - (5 x 28) + 5 = 720 + 1,093.75 - 140 + 5, which is about 1,679 kcal a day at complete rest.
What it cannot tell you
- This is an estimate from population averages. Individual metabolic rates vary by roughly 10% either side for reasons the equation cannot see.
- It does not account for body composition. Two people of the same weight with very different muscle mass will have different real rates.
- Thyroid conditions and some medications shift BMR meaningfully.
Frequently asked
- What is the difference between BMR and TDEE?
- BMR is what you burn at complete rest. TDEE is BMR plus everything you actually do — moving, working, training, digesting. TDEE is the number you eat against.
- Should I eat my BMR?
- No. Eating at your BMR means eating as though you spent the day motionless. Use TDEE as your maintenance figure instead.
- Which formula is most accurate?
- Mifflin-St Jeor is generally the most accurate for the general adult population and is what this calculator uses. Katch-McArdle can be better if you know your body-fat percentage.
- Does BMR fall with age?
- Yes, gradually, and the equation reflects that. Losing muscle as you age accounts for a large part of the decline, which is why resistance training helps.