Calculate your Resting Metabolic Rate, the calories you burn at rest, and turn it into a daily calorie target for your activity level.
Your RMR, or resting metabolic rate, is the number of calories your body burns just to keep you alive and ticking over while at rest: breathing, pumping blood, maintaining temperature and running your organs. It is the single biggest piece of your daily calorie burn, and knowing it gives you a realistic foundation for any eating or weight plan. This calculator estimates your RMR from your age, sex, height and weight, then turns it into a daily calorie target.
I lean on resting metabolic rate constantly with clients, because it reframes food in a healthier way. Once you see how many calories your body spends before you have done anything on purpose, extreme diets start to look as unsustainable as they really are.
RMR and BMR are close cousins and are often used interchangeably, but there is a subtle distinction. BMR (basal metabolic rate) is measured under very strict laboratory conditions, after an overnight fast and full rest. RMR (resting metabolic rate) is measured under more relaxed, real-world conditions, so it includes a little of the energy used for digestion and normal resting activity. In practice RMR runs slightly higher than BMR, usually by under 10%, and for everyday planning the two numbers are effectively interchangeable.
The default estimate uses the Mifflin-St Jeor equation, which research has repeatedly found to be the most accurate predictive formula for most adults. If you know your body fat percentage, the calculator also shows a Katch-McArdle estimate, which is based on your lean body mass rather than total weight. Katch-McArdle is often more accurate for lean or very muscular people, since muscle is far more metabolically active than fat.
Your RMR is the floor, not the whole picture. To estimate the calories you actually need in a day, the calculator multiplies your RMR by an activity factor, from 1.2 for sedentary up to 1.9 for very physically active people. That gives your total daily energy needs, which you can then nudge down for fat loss or up for muscle gain. I usually suggest a gentle deficit of around 500 calories for steady, sustainable weight loss rather than anything drastic.
This calculator uses established, peer-reviewed formulas and reference ranges from recognized health and nutrition authorities. Results are estimates for general education, not a medical diagnosis. For decisions about your health, consult a qualified clinician. Reviewed by Jennifer Zoned, PhD, Nutrition Researcher.
They measure almost the same thing: the calories your body burns at rest. BMR is measured under stricter lab conditions, while RMR is measured under more relaxed conditions and includes a little digestion and resting activity, so RMR is usually slightly higher (typically under 10%). For everyday planning the two are effectively interchangeable.
The Mifflin-St Jeor equation is considered the most accurate for most adults, which is why it is the default here. If you know your body fat percentage, the Katch-McArdle formula (based on lean body mass) can be more accurate for lean or very muscular people, so the calculator shows both when you enter body fat.
First find your daily calorie needs by multiplying RMR by your activity factor. Then eat in a moderate deficit, often around 500 calories a day, for steady loss of roughly half a kilo a week. Avoid eating below your RMR for long periods, since very low intakes are hard to sustain and can cost you muscle.
You have some influence. Building and keeping muscle helps, because muscle is more metabolically active than fat, so strength training and adequate protein support a healthier resting metabolism. Not under-eating for long stretches matters too. Large, permanent jumps in RMR are uncommon, so focus on sustainable habits.
