Clinical BMR Calculator

Your basal metabolic rate is the amount of energy your body spends doing nothing at all. Even at complete rest, the body is busy: the heart pumps, the lungs move, the brain fires, tissues repair themselves and a stable temperature is held. Added together, that constant background work is your BMR, measured in calories per day. For most people it is the single largest slice of daily energy use — often well over half — which is why it makes such a useful starting point for understanding how much you actually need to eat.

BMR is sometimes used interchangeably with resting metabolic rate (RMR). The two are measured under slightly different conditions and RMR runs a little higher, but for everyday planning the numbers are close enough to treat as one. What matters is that this figure is your floor — the energy you would use lying still for a whole day — not your total need.

Clinarix estimates your BMR with the Mifflin–St Jeor equation: 10 × weight in kilograms, plus 6.25 × height in centimetres, minus 5 × age in years, plus a small constant that is +5 for men and −161 for women. If you prefer imperial units the calculator converts your entries first, so the result is identical either way. A 32-year-old man weighing 78 kg at 178 cm works out at roughly 1,738 kcal per day.

Mifflin–St Jeor is the default here for a simple reason: across the common predictive equations, it has the smallest average error against laboratory measurement for healthy, non-obese adults, which is why it is the equation most clinicians and sports dietitians reach for. To turn the resting figure into the number a calorie plan actually uses, the calculator also multiplies your BMR by an activity factor between 1.2 and 1.9 — giving your maintenance energy, or TDEE, for each activity level.

On its own, BMR is best read as context rather than a target. Almost nobody spends the day at complete rest, so eating only your BMR would leave you under-fuelled. The practical number is your maintenance energy — BMR times your activity factor — which is the intake that holds your weight steady. From there, eating consistently below maintenance moves weight down over time and eating above it moves weight up; the size of that gap sets the pace.

Because BMR is built only from your basic measurements, it slots neatly into the rest of your Clinarix profile. Pair it with your TDEE and protein targets to plan a sustainable rate of change, and re-check it whenever your weight shifts meaningfully, since the estimate moves with your body. Saved to your Wellness Snapshot, BMR becomes a baseline you can watch over time rather than a one-off number.