How Do I Know My Resting Metabolic Rate? Methods for Calculation

November 30, 2025 •

5 min read

Your body uses between 60% and 70% of its total daily energy to perform basic, life-sustaining functions while at rest. Knowing your resting metabolic rate (RMR) is key to understanding this baseline energy expenditure and effectively managing your weight and fitness goals.

Quick Summary

This guide covers the various ways to determine your resting metabolic rate (RMR), from highly accurate lab tests to practical at-home estimations using formulas. Learn how to apply your RMR to better understand your body's energy needs for health.

Key Points

Accuracy varies: Highly accurate RMR measurements require a clinical setting with indirect calorimetry, while at-home estimates use predictive equations.
Use equations at home: The Mifflin-St Jeor and Harris-Benedict equations are common formulas for estimating your RMR based on age, sex, height, and weight.
RMR is a baseline: Your RMR represents the calories burned at rest, providing the foundation for calculating your total daily energy needs based on activity levels.
Building muscle helps: Increasing your lean body mass through strength training is one of the most effective ways to naturally increase your RMR.
RMR is dynamic: Factors like age, body composition, diet, and sleep quality can all influence your RMR over time.
RMR vs. BMR: RMR is typically used more often as it's measured under less strict conditions, while BMR is measured under very stringent, fasted, and fully rested conditions.
Personalize your plan: Your RMR is a vital tool for personalizing nutrition and fitness strategies, moving beyond generic advice towards a data-driven approach.

What is Resting Metabolic Rate (RMR)?

Resting Metabolic Rate (RMR) is the amount of energy (calories) your body burns at rest to maintain essential physiological functions, such as breathing, blood circulation, and organ function. It is often used interchangeably with Basal Metabolic Rate (BMR), but there is a subtle distinction. RMR is measured under less restrictive conditions than BMR, typically following an overnight fast but without the strict, full-sleep conditions required for BMR. For most practical purposes, particularly for general health and fitness, RMR is the more accessible and relevant metric. Your RMR is the foundational element of your total daily energy expenditure (TDEE), the total number of calories your body burns in a day when factoring in physical activity. Knowing this baseline number is a powerful tool for weight management, allowing you to create a personalized, data-driven plan for calorie intake and exercise.

The Gold Standard: Laboratory Testing

For the most accurate and precise measurement of your RMR, laboratory testing is the gold standard. These methods take individual factors like body composition and current metabolic function into account, which simple equations cannot fully capture.

Indirect Calorimetry

This is the most common lab-based method for measuring RMR. A person breathes into a device called a metabolic cart, which measures the volume of oxygen consumed and carbon dioxide produced. Based on the principles of gas exchange, the test calculates your body's energy expenditure in real-time. An indirect calorimetry test is typically non-invasive, takes around 15–20 minutes, and requires a period of fasting and rest beforehand to ensure accuracy.

Direct Calorimetry

Direct calorimetry measures the heat produced by the body, as burning calories creates heat. The person stays in a tightly controlled, insulated chamber for an extended period, which is why this method is primarily used for research and is not widely accessible.

How to Calculate Your RMR at Home

For a convenient estimate, several mathematical formulas can be used to calculate your RMR without a trip to a lab. These equations use factors like age, gender, height, and weight to provide a surprisingly accurate starting point, though they may not account for individual metabolic differences.

The Mifflin-St Jeor Equation

Widely regarded as one of the most accurate predictive equations for the general population, the Mifflin-St Jeor formula is a reliable tool for estimating RMR.

For males: RMR = (10 x weight in kg) + (6.25 x height in cm) – (5 x age in years) + 5
For females: RMR = (10 x weight in kg) + (6.25 x height in cm) – (5 x age in years) – 161

The Harris-Benedict Equation

This older equation, developed in 1919 and revised in 1984, can also provide a solid estimate.

For males: RMR = 66.47 + (13.75 × weight in kg) + (5.003 × height in cm) – (6.755 × age in years)
For females: RMR = 447.593 + (9.247 × weight in kg) + (3.098 × height in cm) – (4.330 × age in years)

Factors Influencing Your RMR

While equations provide a useful average, your personal RMR is influenced by several factors, including some you cannot change.

Age: Metabolism naturally slows with age due to muscle mass loss.
Gender: Men typically have higher RMRs than women due to more muscle mass.
Body Composition: Muscle tissue burns more calories at rest than fat tissue, so a higher muscle-to-fat ratio increases RMR.
Genetics: Your metabolic rate is partially predetermined by genetics.
Hormones: Thyroid hormones play a significant role in regulating metabolism.
Diet: Severe calorie restriction can cause a metabolic slowdown as the body tries to conserve energy.
Sleep: Lack of quality sleep can negatively impact RMR and hormone regulation.

RMR vs. BMR: A Comparison


Feature	Resting Metabolic Rate (RMR)	Basal Metabolic Rate (BMR)
Measurement Condition	Measured after a period of rest and fasting, but conditions are less stringent.	Measured under very strict, rested, and fasted conditions, typically in a clinical setting.
Practicality	Easier to measure and more widely accessible for general fitness.	Reserved for more precise medical or research purposes.
Energy Expenditure	Includes some minor energy expenditure for minimal activity (e.g., digestion), making it slightly higher.	Represents the absolute minimum energy needed for vital functions, making it slightly lower.
Primary Use	Estimating daily calorie needs for diet planning and weight management.	Scientific research and detailed physiological assessments.

Strategies to Optimize Your Resting Metabolic Rate

While genetics and age play a role, you can make positive lifestyle changes to support and increase your RMR. Building a higher RMR means your body burns more calories even at rest, which can aid in weight management.

Build Lean Muscle Mass: As muscle is more metabolically active than fat, lifting weights and resistance training is one of the most effective ways to increase your RMR over time.
Eat Enough Protein: The 'thermic effect of food' (TEF) means your body burns calories just to digest, absorb, and process nutrients. Protein requires significantly more energy to process than fats or carbs, temporarily boosting your metabolism.
Stay Hydrated: Drinking sufficient water is crucial for metabolic processes to function properly. Even mild dehydration can cause your metabolism to slow.
Prioritize Sleep: Sleep deprivation can negatively affect hormones that regulate appetite and metabolic function. Aim for 7–9 hours of quality sleep per night.
Manage Stress: Chronic stress can elevate cortisol levels, which is linked to a slower metabolism and increased fat storage. Mindfulness and relaxation techniques can help.
Avoid Extreme Calorie Restriction: Drastic, low-calorie diets signal to your body that it's in a starvation state. In response, your metabolism slows to conserve energy, making long-term weight loss difficult.

Conclusion

Knowing your resting metabolic rate is a powerful foundation for personalizing your health and wellness journey. Whether you use the precise, lab-based indirect calorimetry method or a reliable at-home formula like the Mifflin-St Jeor equation, gaining this insight removes much of the guesswork from managing your calorie intake. Armed with your RMR, you can make informed decisions about your diet and exercise to effectively reach and maintain your weight goals. Remember that your metabolism is dynamic, so regularly reassessing and adapting your approach as your body and lifestyle change is key to long-term success.

For more detailed information on measuring metabolic rate, consider exploring resources from the National Institutes of Health (NIH) or consulting with a healthcare professional.

This content is for informational purposes only and is not medical advice. Consult a healthcare professional before making changes to your diet or exercise plan.

Frequently Asked Questions

RMR (Resting Metabolic Rate) and BMR (Basal Metabolic Rate) both measure calories burned at rest. However, RMR is measured under slightly less restrictive conditions and is generally more practical for everyday use, while BMR requires a strict, clinical, and completely rested state.

At-home calculations using formulas like the Mifflin-St Jeor or Harris-Benedict equation are estimates based on population averages. They can provide a useful starting point but are not as precise as laboratory-based indirect calorimetry, which accounts for individual body composition.

Yes. By knowing your RMR, you can accurately calculate your Total Daily Energy Expenditure (TDEE) and determine a target daily caloric intake to create a calorie deficit. This allows for a more personalized and effective weight loss plan.

Your RMR is influenced by factors including your age, gender, genetics, and body composition (muscle-to-fat ratio). It can also be affected by hormones, diet, activity levels, and sleep patterns.

Indirect calorimetry is a lab-based test considered the gold standard for measuring RMR. It works by analyzing the volume of oxygen you consume and carbon dioxide you produce while at rest. This gas exchange data is used to calculate your precise caloric expenditure.

You can increase your RMR naturally by building lean muscle mass through strength training, consuming a diet rich in protein, staying well-hydrated, and getting sufficient sleep. Avoiding extreme calorie restriction is also important.

It is generally recommended to reassess your RMR every 3 to 6 months, or after significant lifestyle changes such as gaining or losing a substantial amount of weight, changing your exercise routine, or adjusting your diet.

Online calculators typically use predictive equations, such as Mifflin-St Jeor, to provide an estimate. They are a convenient tool but may not be accurate for everyone, especially those with significantly higher-than-average muscle mass or other unique metabolic factors.