Mifflin-St Jeor Calculator

The Mifflin-St Jeor equation was published in 1990 and has become the standard starting point for estimating resting energy needs. It reads weight in kilograms, height in centimetres and age in years, then applies a single sex term: men add five calories to the result, women subtract a hundred and sixty-one. Written out, a man’s BMR is ten times weight plus six-and-a-quarter times height, minus five times age, plus five; a woman’s is the same arithmetic with that final term flipped to minus one hundred and sixty-one. Nothing exotic happens behind the scenes — the calculator is doing that one line of multiplication and addition with the numbers you type. Because the equation was derived from a comparatively modern group of people, it tends to sit closer to what a metabolic cart would actually measure than the older formulas that preceded it, which is why it is the figure most clinicians and fitness apps quote when no other formula is specified.

A BMR on its own only describes a body lying still. To turn it into the number you actually plan meals around, the calculator multiplies it by an activity factor — 1.2 for a sedentary week, rising in steps to 1.9 for someone training hard twice a day. That product is your Total Daily Energy Expenditure, the maintenance figure where weight holds steady. The same Mifflin-St Jeor BMR therefore produces very different daily totals depending on the multiplier you choose, which is why the activity step matters as much as the formula. If you want the resting figure on its own without the activity layer, the BMR Calculator shows just that; for the full daily picture with every activity tier laid out, the TDEE Calculator is the parent tool this page is built from.

Mifflin-St Jeor is accurate to within roughly ten per cent of a measured metabolic rate for most non-obese adults — the standard it earned in a 2005 systematic review (Frankenfield et al.) — which is close enough to plan around but not a precise reading of your own physiology. Two people with identical height, weight, age and sex can still burn meaningfully different amounts because of muscle mass, genetics and hormones the equation never sees, and the activity multiplier is a self-reported guess that most people round upward. Treat the output as a well-grounded starting estimate: hold to it for a couple of weeks, watch how your weight actually responds, and adjust the intake rather than the formula. When you are ready to convert the maintenance number into a fat-loss target, the Calorie Deficit Calculator does that step. These figures are general estimates for healthy adults, not medical advice.