A BMR Calculator computes bmr from the inputs you provide. It applies the standard formula to the values you enter and returns the result instantly, without sending any data to a server. Enter weight, height, age and sex to find your daily resting calories.
Basal metabolic rate is the energy your body uses at rest.
Mifflin-St Jeor: Male = 10w + 6.25h - 5a + 5; Female = 10w + 6.25h - 5a - 161. TDEE = BMR x activity factor.
Calculate Basal Metabolic Rate with the Mifflin-St Jeor and Harris-Benedict equations.
Your Basal Metabolic Rate is the energy your body uses at complete rest to maintain vital functions like breathing, circulation, and cell repair. This calculator computes BMR using both the modern Mifflin-St Jeor equation and the revised Harris-Benedict equation so you can compare results. BMR usually represents 60 to 70 percent of total daily energy expenditure (TDEE).
W is weight in kilograms, H is height in centimeters, and A is age in years. The Mifflin-St Jeor equation, published in 1990, is preferred by the Academy of Nutrition and Dietetics. We multiply by 1.2, 1.55, and 1.725 to estimate TDEE for sedentary, moderate, and active lifestyles.
Three numbers often confused; they answer different questions:
| Metric | Formula | What it tells you |
|---|---|---|
| BMI (Body Mass Index) | weight kg / height m^2 | Rough screen for under/normal/over weight. Bad for athletes. |
| BMR (Basal Metabolic Rate) | Mifflin-St Jeor equation | Calories your body burns AT REST in 24 hours |
| TDEE (Total Daily Energy Expenditure) | BMR x activity multiplier | Total calories burned per day, including activity |
| Body fat % | DEXA / calipers / bioimpedance | More accurate than BMI for athletes and very lean people |
| Category | BMI range | Notes |
|---|---|---|
| Underweight | < 18.5 | Increased risk of malnutrition, osteoporosis |
| Normal | 18.5 - 24.9 | Lowest health risk for most adults |
| Overweight | 25.0 - 29.9 | Increased risk of cardiovascular disease, diabetes |
| Obese class I | 30.0 - 34.9 | High risk; lifestyle change recommended |
| Obese class II | 35.0 - 39.9 | Very high risk; clinical intervention often warranted |
| Obese class III | >= 40.0 | Extreme risk; bariatric options often discussed |
South Asians have higher cardiovascular risk at lower BMI. India, Singapore, and many Asian countries use:
The simplified energy balance:
To lose 0.5 kg / 1 lb per week, eat ~500 kcal/day below TDEE. To gain muscle, eat 200-500 kcal/day above TDEE with adequate protein (~1.6g per kg body weight per day) and resistance training.
Caveats:
| Macronutrient | Daily target | Energy density |
|---|---|---|
| Protein | 0.8 g/kg sedentary; 1.6-2.2 g/kg if exercising | 4 kcal/g |
| Fat | 20-35% of total calories; minimum ~0.5 g/kg | 9 kcal/g |
| Carbohydrate | Fills the rest; minimum 130 g/day for brain function | 4 kcal/g |
| Fiber | 25-38 g/day | ~2 kcal/g (variable) |
| Water | 30-40 ml/kg body weight | 0 kcal/g |
Basal Metabolic Rate is the calories your body burns at complete rest to maintain vital functions like breathing and circulation. It accounts for 60 to 70 percent of total daily energy expenditure.
The Mifflin-St Jeor equation is generally the most accurate for the modern population and is recommended by the Academy of Nutrition and Dietetics. Harris-Benedict tends to slightly overestimate BMR.
Multiply BMR by an activity factor (1.2 sedentary to 1.9 very active) to get TDEE, then subtract 500 kcal/day for about 1 lb/week loss. Avoid eating below BMR for long periods.
Yes. BMR declines about 1 to 2 percent per decade after age 20 due to loss of lean body mass. Strength training preserves muscle and slows the decline.
BMI is a population screening tool, not an individual diagnosis. It overestimates body fat in muscular athletes and underestimates it in people with low muscle mass. Body fat percentage (DEXA, calipers) is more accurate. Waist-to-height ratio under 0.5 is another useful single number.
0.5-1 kg (1-2 lb) per week is sustainable for most adults. Faster loss is possible but typically comes from water, glycogen, and muscle - not just fat. Crash diets also slow metabolism and rebound when normal eating resumes.
BMR estimates are within ±10% of measured rates for most people. TDEE depends on self-reported activity, which is usually overestimated by 20-50%. Track actual weight change over 2-4 weeks and adjust intake to match.
Almost all daily fluctuation is water (sodium, carbohydrate storage as glycogen which holds 3-4x its weight in water) and digestive contents. Fat loss is on the order of 100-150g per day at most. Weigh weekly at the same time for trend, not daily.
For weight loss, the two are equivalent if total calories are the same. Some people find fasting easier to comply with (skipping breakfast = automatic deficit). Others find it harder. The best diet is the one you can sustain.
It applies the standard formula. Accuracy is limited only by your input precision. For decisions with material consequences (taxes, medical, legal, structural), use the result as a starting point and verify with a qualified professional in the relevant field.
Yes. 100% free, no signup, no payment, no API key. The site is funded by display ads around the tool but not inside the calculation flow.
No. All inputs stay in your browser tab. Closing the tab discards them. The site uses Google Analytics for traffic measurement (anonymized) but the analytics never see what you type into the form.
Yes. The tool is responsive and tested on iOS Safari, Android Chrome, and major desktop browsers. Touch targets meet Apple's 44pt and Google's 48dp minimum.
Yes. Once the page has loaded, it works without internet. The calculation runs in JavaScript on your device.
Email hi@3tej.com with the URL of this page and a description of what you saw vs expected. We typically respond within 72 hours.
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Most likely: different formula assumptions, different default values, different rounding rules, or different applicable rates. Check the methodology if both tools document it. Both can be valid for different scenarios.