BMR Calculator (Mifflin-St Jeor, Harris-Benedict)
Your basal metabolic rate from eight published equations, in kcal and kJ.
All equations for you
| Equation | kcal/day | kJ/day |
|---|
How it was calculated
To turn BMR into the calories you need in a day, multiply by your activity level — try the TDEE calculator.
For general information only, not medical advice. Consult a qualified health professional for advice about your situation.
About the BMR Calculator (Mifflin-St Jeor, Harris-Benedict)
Your basal metabolic rate (BMR) is the energy your body uses in a day just to stay alive at complete rest — breathing, circulation, keeping warm, running your organs. It is measured lying down, awake, after 10–12 hours without food and 8 hours of rest, in a room that is neither warm nor cool. Depending on age and lifestyle it is 45–70% of all the energy you use in a day (FAO/WHO/UNU, 2004).
Nobody can measure BMR with a formula, so this calculator shows eight published prediction equations side by side, in kcal and kJ: Mifflin-St Jeor (the default), the original and revised Harris-Benedict, Henry (Oxford), Schofield (FAO/WHO/UNU), the ICMR-NIN adjustment for Indian adults, and — if you know your body-fat percentage — Katch-McArdle and Cunningham. The spread between them shows how uncertain any single estimate is.
How to use it
- Choose male or female, then enter your age, weight and height (switch to lb · ft/in if you prefer).
- Optionally add your body-fat % (from a scan, a smart scale or the body fat calculator) to unlock the lean-mass equations.
- Read the Mifflin-St Jeor result at the top, then compare the other equations in the table. Under How it was calculated, pick an equation to see its formula with your numbers.
- Copy the table or download it as CSV. To turn BMR into daily calories, multiply by your activity level — the TDEE calculator does that for you.
Examples
Mifflin-St Jeor 1,780 kcal/day (7,448 kJ) · Harris-Benedict revised 1,854 · original 1,865 · Henry 1,745 · Schofield 1,791 · ICMR-adjusted 1,612
Mifflin-St Jeor 1,345 kcal/day · Harris-Benedict revised 1,405 · Henry 1,352 · Schofield 1,376
Katch-McArdle 1,839 kcal/day · Cunningham 1,996 kcal/day
The equations
Weight in kg, height in cm (Henry: metres), age in years; results in kcal per day.
- Mifflin-St Jeor (1990): 10 × weight + 6.25 × height − 5 × age + 5 for men, − 161 for women
- Harris-Benedict, revised (Roza & Shizgal, 1984): men 88.362 + 13.397 × weight + 4.799 × height − 5.677 × age; women 447.593 + 9.247 × weight + 3.098 × height − 4.330 × age
- Harris-Benedict, original (1919): men 66.473 + 13.7516 × weight + 5.0033 × height − 6.755 × age; women 655.0955 + 9.5634 × weight + 1.8496 × height − 4.6756 × age
- Henry (Oxford, 2005): weight and height coefficients that change with age band (18–29, 30–59, 60+; teenage bands too), in MJ/day — for example men aged 30–59: 0.0476 × weight + 2.26 × height (m) − 0.574
- Schofield (FAO/WHO/UNU 2004): weight only, by age band — for example men 30–59: 11.472 × weight + 873.1
- ICMR-NIN 2020 adjustment: Schofield × 0.90 for Indian adults
- Katch-McArdle: 370 + 21.6 × lean mass (kg) · Cunningham (1980): 500 + 22 × lean mass, where lean mass = weight × (1 − body fat %)
1 kcal = 4.184 kJ, so 1 MJ = 239.006 kcal.
Which equation should I use?
- Mifflin-St Jeor is the best general choice. A systematic review for the American Dietetic Association (Frankenfield 2005) found it predicted resting metabolic rate within 10% of the measured value in more people of normal weight and with obesity than any other common equation, with the narrowest error range. It was derived from 498 adults aged 19–78 (Mifflin).
- Henry (Oxford) was developed because the older Schofield equations can overestimate BMR in many populations. The UK uses it for its energy reference values (SACN 2011), where it performed slightly better than Schofield. It also covers teenagers, so it is the headline for ages 10–17.
- Harris-Benedict is the classic. Mifflin et al. found the 1919 version overestimated measured values by about 5%, and Roza & Shizgal put its precision at about ±14%.
- Schofield underpins the FAO/WHO/UNU (2004) requirements. ICMR-NIN found these equations can overestimate BMR in Indian adults by 10–12% and lowered them by 5% and then a further 5% for its 2020 recommendations.
- Katch-McArdle and Cunningham use lean body mass, which Mifflin et al. found to be the strongest single predictor of resting energy use. They suit people who know their body-fat percentage — for example very lean or muscular people.
How accurate is a predicted BMR?
For a group of people the equations work well; for one person they can be off by 10% or more. In the US dataset that SACN used to compare equations, Henry predicted within ±10% of the measured value for 73% of people and Schofield for 69% — so roughly one person in four is outside ±10%. Older adults and many ethnic groups were under-represented in the studies behind most equations. That is why the result shows a ±10% range; only indirect calorimetry measures your actual rate.
Sources
- Mifflin MD et al. A new predictive equation for resting energy expenditure, Am J Clin Nutr 1990;51:241-7
- Roza AM, Shizgal HM. The Harris Benedict equation reevaluated, Am J Clin Nutr 1984;40:168-82
- SACN, Dietary Reference Values for Energy, Appendix 4 — Henry and Schofield coefficients and their accuracy
- FAO/WHO/UNU, Human energy requirements, Table 5.2 — Schofield equations
- ICMR-NIN, Brief note on Nutrient Requirements for Indians 2020
- Frankenfield D et al. Comparison of predictive equations for resting metabolic rate, J Am Diet Assoc 2005;105:775-89
Limitations
- Predictions, not measurements: individual BMR can differ from every equation by 10% or more.
- Mifflin-St Jeor and Harris-Benedict were developed in adults; for 10–17-year-olds only Henry and Schofield (which have teenage age bands) are shown.
- The equations do not adjust for illness, fever, pregnancy, thyroid conditions or medicines that change metabolism.
- Body-fat percentages from home scales and tape methods are themselves estimates, which carries into Katch-McArdle and Cunningham.
Privacy
Everything happens in your browser. What you enter or open here is not uploaded or stored by MySmartCoPilot.
Frequently asked questions
What is the difference between BMR and RMR?
BMR is measured under strict conditions — lying down, awake, after 10–12 hours without food and 8 hours of rest, in a thermoneutral room. Resting metabolic rate (RMR, or resting energy expenditure) is measured under less strict conditions, so it can be slightly higher. Mifflin-St Jeor was derived from resting energy expenditure; in practice the two terms are used interchangeably for these equations.
Is BMR the number of calories I should eat?
No. BMR is only the energy used at complete rest. You also use energy to digest food and to move, so your daily needs are your BMR multiplied by a physical activity level — typically 1.4 to 2.0. Use the TDEE calculator for that, and the calorie deficit planner if you want to lose weight.
Why do the equations give different answers?
Each was fitted to a different group of people: Harris-Benedict to 239 mostly young adults more than a century ago, Mifflin-St Jeor to 498 adults aged 19–78, Schofield and Henry to thousands of BMR measurements collected from many studies. The spread in the table — often 150–250 kcal — is an honest picture of the uncertainty.
Which equation is best for Indians?
ICMR-NIN found that the FAO/WHO/UNU (Schofield) equations overestimate BMR in Indian adults by 10–12% and uses them reduced by about 10%; that row is shown as "Schofield − 10%". Mifflin-St Jeor is also reasonable — compare both and treat the result as a range.
Does muscle raise BMR?
Yes. Lean tissue uses far more energy at rest than fat — the NIH body-weight model behind the calorie deficit planner counts about 22 kcal per kg of lean tissue a day against 3.2 kcal per kg of fat. That is why the lean-mass equations (Katch-McArdle, Cunningham) can give a higher BMR for a muscular person of the same weight.