How to estimate your BMR
Choose the male or female coefficient, then enter your age, weight and height. The page is for adults 18 and older. Use a recent measured weight rather than a goal weight, and in U.S. mode enter height as total inches (5 feet 10 inches is 70).
The result is resting energy only. It doesn't include any activity. For your daily total, use the TDEE calculator, which multiplies this number by an activity factor.
- Pick the male or female coefficient.
- Enter your age in whole years.
- Choose metric (kg, cm) or U.S. customary (lb, total inches).
- Enter weight and height and calculate.
- Check the step-by-step ledger and the Harris-Benedict comparison.
Mifflin-St Jeor and Harris-Benedict formulas
Both equations need weight in kilograms, height in centimetres and age in years. The calculator converts pounds and inches first. Results are in kcal per day, and one food Calorie is one kcal.
Mifflin and colleagues published their equation in 1990 after measuring resting energy in 498 healthy adults aged 19 to 78. Roza and Shizgal published the revised Harris-Benedict coefficients in 1984.
Mifflin-St Jeor, men: 10 x weight + 6.25 x height - 5 x age + 5Mifflin-St Jeor, women: 10 x weight + 6.25 x height - 5 x age - 161Revised Harris-Benedict, men: 88.362 + 13.397 x weight + 4.799 x height - 5.677 x ageRevised Harris-Benedict, women: 447.593 + 9.247 x weight + 3.098 x height - 4.330 x ageKilojoules per day = kcal per day x 4.184
Worked BMR examples
For a 30-year-old man at 75 kg and 178 cm, Mifflin-St Jeor gives 1,717.5 kcal a day, about 7,186 kJ. Revised Harris-Benedict gives about 1,777.0, roughly 59.5 kcal (3.5%) higher.
For a 40-year-old woman at 65 kg and 165 cm, Mifflin-St Jeor gives 650 + 1,031.25 - 200 - 161 = 1,320.25 kcal a day. Harris-Benedict gives about 1,386.6. The gap between equations is a reminder that each one is an estimate.
| Part | Math | Value | Running total |
|---|---|---|---|
| Weight | 10 x 75 | 750.0 | 750.0 |
| Height | 6.25 x 178 | 1,112.5 | 1,862.5 |
| Age | -5 x 30 | -150.0 | 1,712.5 |
| Sex constant | +5 | 5.0 | 1,717.5 kcal/day |
BMR vs TDEE
BMR is what you'd burn lying still all day. TDEE, your total daily energy expenditure, adds digestion and every bit of movement on top. That's why your TDEE is always higher than your BMR.
For the man in our example, a BMR of 1,717.5 becomes about 2,061 kcal with the lowest activity factor of 1.2, and about 2,662 with a moderate 1.55. Plan your eating around TDEE. BMR is just the base it's built on.
| Term | What it covers | Includes activity? |
|---|---|---|
| BMR | Energy at complete rest under strict lab conditions | No |
| RMR or REE | Energy at rest under looser conditions, usually a bit higher | No |
| TDEE | Energy across the whole day | Yes |
Basal metabolic rate vs resting metabolic rate
Strictly, basal metabolic rate is measured after sleep, fasting and complete rest. Resting metabolic rate, or resting energy expenditure, is measured under looser conditions and is often slightly higher. Most websites use BMR and RMR as if they mean the same thing.
Mifflin-St Jeor was built to predict resting energy expenditure. This page calls the result BMR because that's what people search for, but it's technically a resting estimate.
How each input changes your BMR
Holding the other inputs fixed, Mifflin-St Jeor adds 10 kcal for every extra kilogram and 6.25 kcal for every extra centimetre, and takes away 5 kcal for every year of age. These are averages from the study group, not a forecast of how your body will change.
Muscle matters more than the equation can show. People with more lean mass usually burn more at rest, and the calculator has no way to know your body composition.
Limits: this is an estimate
Mifflin-St Jeor predicts an average for people with your measurements. Validation studies often count an estimate as accurate if it lands within 10% of a measured value, and some people still fall outside that. Indirect calorimetry, which measures oxygen used and carbon dioxide breathed out, is the reference when a real number matters.
Don't use this page for children or teens, pregnancy or breastfeeding, eating disorders, serious illness or recent major weight change. Your BMR isn't a calorie target, and eating at or below it isn't a safe plan on your own. Talk to a doctor or registered dietitian if your result raises a question about your health.
Sources
These studies and government sources back up the equations and limits on this page.