Basal metabolic rate
Calculate the calories your body burns at rest with the Mifflin-St Jeor formula. Get your BMR, TDEE maintenance, loss/gain targets and an estimate of how long it takes to reach your goal.
yrs
kg
kg
cm
At rest (BMR)
kcal
Maintenance (With activity)
kcal
Practically, this equals about per day.
📉 To lose
kcal / day
Safe 300 kcal/day deficit.
📈 To gain
kcal / day
🎯 To reach kg, expect about weeks at this healthy pace.
To lose weight, a gentle 300 kcal deficit is applied to prevent fatigue and preserve muscle.
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What is basal metabolic rate (BMR)?
Your body is an engine that constantly consumes energy. Even lying in bed all day, your organs (brain, heart, lungs) need fuel to function. That's the basal metabolic rate (BMR). This number represents about 60 to 75% of your total daily energy expenditure.
Why the Mifflin-St Jeor formula?
Created in 1990, it is considered by most health professionals as the most accurate BMR estimate, outperforming the older Harris-Benedict formula (which overestimates by ~5%).
The calculation works like this:
- Men: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
- Women: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
How to use these numbers?
Weight loss
A gentle 300 kcal/day deficit on your maintenance is ideal: ~0.3 kg/week without excessive hunger or muscle loss.
Stabilization
Eat the number of calories shown in the Maintenance (TDEE) section. Energy in = energy out.
Muscle gain
Add 200 to 300 kcal to your maintenance to build lean tissue without putting on too much fat.
Visual landmarks: what does a meal look like?
Snack
~150 to 200 kcal1 apple + a handful of almonds (15 g), or a greek yogurt with honey.
Light meal
~400 to 500 kcalBig mixed salad (grilled chicken, veggies, quinoa) + 1 fruit.
Standard meal
~600 to 700 kcal150 g meat/fish + 200 g cooked carbs + green veggies + 1 yogurt.
Heavy meal
~900 to 1000+ kcalBurger with fries, a whole pizza, or a saucy dish with dessert.
The 2 pillars to optimize your metabolism
- Hydration: mild dehydration slows the metabolism. Cold water even forces your body to spend a bit of energy to warm it up (thermogenesis).
- Sleep: lack of sleep disrupts hunger hormones (ghrelin, leptin). Aim for 7 to 8 hours per night for effective weight loss.
FAQ
Should I recalculate my BMR often?
Your BMR changes if your weight fluctuates significantly (more than 3-5 kg). It's good to recalculate it every few months if you are in a body transformation process.
Does this calculator account for muscle mass?
No. The Mifflin-St Jeor formula does not separate fat mass from lean mass. If you are a very lean bodybuilder, this formula will underestimate your needs. In that case, the Katch-McArdle formula (which requires knowing your body fat percentage) is more appropriate.
What happens if I eat less than my BMR?
This is strongly discouraged long-term. Eating below your BMR (your vital needs) will slow your metabolism, cause extreme fatigue and muscle loss, and make sustainable weight loss very difficult (yo-yo effect).
What is the difference between BMR and TDEE?
BMR is the minimum energy your body spends at complete rest, just to keep organs running. TDEE adds to that BMR all the energy spent through daily activity (walking, work, exercise). To maintain weight, you target TDEE, not BMR.
Why is the target weight optional?
The "Target weight" field is only used to estimate how many weeks it takes to reach a weight-loss goal. If you just want to know your BMR and maintenance, leave it empty: the two main results show up as soon as you fill age, weight and height.
