RMR Calculator
Estimate your resting metabolic rate (RMR) with Mifflin-St Jeor, Harris-Benedict, and Katch-McArdle formulas. Free RMR calculator with BMR comparison and chart.
About This Calculator
The Resting Metabolic Rate (RMR) Calculator estimates the number of calories your body burns at rest to sustain vital functions like breathing, circulation, brain activity, and digestion. RMR accounts for 60-75% of your total daily energy expenditure (TDEE) and is a crucial metric for weight management, fitness planning, and nutritional assessment. This calculator is designed for adults aged 18 and above of all genders and fitness levels worldwide.
Our RMR calculator uses the validated Mifflin-St Jeor equation (1990), the most accurate general-purpose formula for estimating basal metabolic rate, and applies a 10% adjustment for the thermic effect of food to derive RMR. For comparison, we also provide results using the Harris-Benedict equation (1919) and the Katch-McArdle formula (which uses lean body mass for athletes). The Mifflin-St Jeor formula is: Male BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age) + 5; Female BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age) - 161; RMR = BMR × 1.10.
Regional Notes
India (IN): The Indian Council of Medical Research (ICMR) recommends using the Mifflin-St Jeor formula for Indian populations. Average adult RMR in India ranges from 1,100-1,800 kcal/day depending on body composition. The National Institute of Nutrition, Hyderabad, provides updated RMR reference values in their Dietary Guidelines for Indians (2023).
United States (US): The National Institutes of Health (NIH) and the Academy of Nutrition and Dietetics endorse the Mifflin-St Jeor equation as the preferred formula for clinical use. The average RMR for American adults is approximately 1,400-2,000 kcal/day based on NHANES survey data.
United Kingdom (UK): The British Dietetic Association (BDA) and the Scientific Advisory Committee on Nutrition (SACN) recommend Mifflin-St Jeor for RMR estimation in clinical practice. The UK average RMR for adults ranges from 1,300-1,900 kcal/day according to the National Diet and Nutrition Survey (NDNS).
Frequently Asked Questions
What is RMR and how is it different from BMR?
Resting Metabolic Rate (RMR) is the number of calories your body burns at rest, including the thermic effect of food (digestion adds 5-10%). Basal Metabolic Rate (BMR) is measured under stricter conditions — after 24 hours of rest and an overnight fast — and does not include digestion. RMR is typically about 10% higher than BMR and is considered more practical for everyday use.
Which RMR formula is most accurate?
The Mifflin-St Jeor equation, developed in 1990, is considered the most accurate general-purpose RMR formula. It predicts RMR within ±10% of measured values for most people. The Harris-Benedict equation (1919) is slightly less accurate but still widely used. The Katch-McArdle formula is most accurate for athletes and lean individuals as it accounts for lean body mass.
How many calories do I burn at rest?
An average adult burns between 1,200 and 2,000 calories per day at rest, depending on age, sex, weight, height, and muscle mass. For example, a 30-year-old male weighing 80 kg and 180 cm tall has an RMR of approximately 2,050 kcal/day. RMR accounts for 60-75% of total daily energy expenditure.
What factors affect resting metabolic rate?
Several factors influence RMR: muscle mass (more muscle increases RMR), age (RMR decreases about 1-2% per decade after age 20), genetics, climate (cold environments increase RMR), meal frequency, pregnancy, and crash-dieting (which decreases RMR). Men typically have higher RMR than women due to greater muscle mass.
Is RMR testing accurate?
The most accurate way to measure RMR is through indirect calorimetry at a licensed facility, where you breathe into a device for about 10 minutes. This procedure is expensive but accurate within ±100-200 calories. Online RMR calculators are a free alternative with an accuracy of approximately ±300 calories for most people.
How can I use RMR for weight loss?
To lose weight, consume slightly more calories than your RMR but fewer than your total daily energy expenditure (TDEE). Your RMR represents the minimum calories needed for survival. A deficit of 300-500 calories below TDEE typically leads to 0.5-1 kg (1-2 lbs) of weight loss per week. Always consult a healthcare professional before starting a diet.
Does a keto diet or fasting affect RMR?
Current research suggests that a very low-calorie ketogenic diet does not significantly alter RMR in obese patients who lose about 20 kg. However, long-term crash-dieting and severe calorie restriction can decrease RMR, making weight loss harder. Intermittent fasting does not appear to significantly affect RMR either, though research is still limited.