Free online tool
BMR Calculator
Estimate your Basal Metabolic Rate (BMR) and total daily energy expenditure (TDEE).
What is BMR?
BMR is the number of calories your body burns at complete rest, just to keep your organs running. It accounts for around 60–75% of the calories most people burn in a day. This calculator uses the Mifflin-St Jeor equation, the modern standard endorsed by dietitians because it's more accurate for the general population than older formulas.
Using TDEE for weight goals
Multiply BMR by an activity factor to get TDEE — total daily energy expenditure. Eat that many calories to maintain weight, subtract roughly 500 per day to lose about half a kilogram per week, or add 250–500 for lean bulking. Treat the number as a starting estimate and adjust based on how your body actually responds over a few weeks.
+How accurate is this?
Within about 10% for most healthy adults. Very muscular or very lean individuals may need a body-composition-based formula for more accuracy.
+Should I go below my BMR to lose weight faster?
No. Eating well below your BMR long-term causes muscle loss and hormonal issues. A moderate deficit is more sustainable.
Estimating the calories your body burns at rest
Basal Metabolic Rate is the energy your body needs just to keep organs running, breathing and maintaining temperature while completely at rest, before you've taken a single step or lifted a fork. This calculator uses the Mifflin-St Jeor equation, which for men is 10 times weight in kilograms plus 6.25 times height in centimetres minus 5 times age plus 5, and for women the same terms but minus 161 instead of plus 5.
Mifflin-St Jeor replaced the older Harris-Benedict equation in most modern nutrition guidance because studies found it more accurate on average across a broad range of body types, though like any regression formula it was still built from averages across many people rather than tailored to any one person's metabolism.
Turning BMR into a daily calorie target
BMR alone isn't what you burn in a normal day, so it gets multiplied by an activity factor: around 1.2 for a mostly sedentary lifestyle, 1.375 for light exercise a few times a week, 1.55 for moderate daily activity, and up to 1.9 for very intense training schedules. That final number is your Total Daily Energy Expenditure, the figure most people actually use for weight goals.
Worked example
A 30-year-old woman weighing 65 kg and standing 165 cm tall has a BMR of (10 x 65) + (6.25 x 165) - (5 x 30) - 161, which works out to 650 + 1031.25 - 150 - 161 = 1370.25 calories per day at rest. With a moderately active multiplier of 1.55, her estimated daily needs come to roughly 2124 calories.
A 30-year-old man of the same weight and height would use plus 5 instead of minus 161, giving a BMR of about 1687 calories at rest — a difference driven purely by the formula's sex-based adjustment for typical differences in muscle mass and body composition.
Using BMR for weight goals responsibly
A commonly cited rule is that a sustained daily deficit of roughly 500 calories below Total Daily Energy Expenditure corresponds to about half a kilogram of fat loss per week, though real-world results vary with water retention, muscle changes and individual metabolism. Cutting too aggressively below BMR itself, rather than below total expenditure, risks nutrient shortfalls and a slower long-term metabolism.
Where this stops being reliable
Mifflin-St Jeor is a population average and doesn't account for individual muscle mass, hormonal conditions or metabolic adaptations from past dieting, so this figure is a starting estimate for general planning, not personalised medical or nutritional advice — anyone with a health condition affecting metabolism should check with a clinician or registered dietitian before making significant dietary changes.
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