What is my resting energy use and how do I calculate it?

November 19, 2025 •

4 min read

Resting energy use, or resting metabolic rate (RMR), accounts for about 60–70% of your total daily energy expenditure. This is the energy your body burns at rest to perform essential life-sustaining functions like breathing, circulation, and cell production. Knowing this baseline figure is a foundational step toward understanding your body's unique energy requirements.

Quick Summary

This guide explains the concept of resting energy use, or Resting Metabolic Rate (RMR), detailing the factors influencing it and how it differs from Basal Metabolic Rate (BMR). It provides instructions for calculating RMR using predictive formulas and describes how to use this metric to set effective weight management goals.

Key Points

Resting vs. Total Energy: Resting energy use (RMR) is the largest component of your total daily calorie burn, accounting for 60–70% of your energy expenditure.
Measurement Methods: While clinical tests like indirect calorimetry are highly accurate, predictive equations like the Mifflin-St Jeor formula offer a practical and reasonably precise estimate for most people.
Key Influencers: Your RMR is affected by factors such as age, sex, body composition (specifically lean muscle mass), genetics, and hormone levels.
Boost Your RMR: Increasing your lean muscle mass through strength training is one of the most effective ways to sustainably increase your resting energy expenditure.
Calorie Restriction Impact: Severely restricting calories can trigger a metabolic slowdown as your body conserves energy. It's more effective to focus on a moderate caloric deficit for sustainable weight loss.
Lifestyle Factors: Getting adequate sleep, staying hydrated, and eating enough protein all contribute to maintaining a healthy and efficient metabolism.
Practical Application: Calculate your RMR and multiply it by an activity factor to get your total daily energy expenditure (TDEE), providing a realistic target for weight management.

What is Resting Energy Use (RMR)?

Your resting energy use, formally known as Resting Metabolic Rate (RMR), is the total number of calories your body burns to maintain basic physiological functions while in a state of rest. These are the calories required for your heart to beat, your lungs to breathe, your body temperature to stay regulated, and your brain to function. It is a critical component of your Total Daily Energy Expenditure (TDEE), typically making up the largest percentage.

This is often used interchangeably with Basal Metabolic Rate (BMR), but there is a slight distinction. While BMR is measured under very strict, clinical conditions—after a full night's sleep and 12-hour fast—RMR is a more practical measurement taken under less restrictive, real-world resting conditions, such as after an overnight fast. For most practical purposes, the terms are similar enough that they can be used interchangeably.

How to Calculate Your Resting Energy Use

There are several equations to estimate your RMR. The most common and widely recommended is the Mifflin-St Jeor equation, which is generally considered more accurate than older formulas.

Mifflin-St Jeor Equation

Men: RMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) + 5
Women: RMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) - 161

For example, a 35-year-old woman who is 165 cm tall and weighs 68 kg would calculate her RMR as follows:

RMR = (10 × 68) + (6.25 × 165) - (5 × 35) - 161 RMR = 680 + 1031.25 - 175 - 161 RMR = 1,375.25 kcal per day

Using RMR to Determine Total Daily Energy Expenditure (TDEE)

Once you have your RMR, you can estimate your TDEE by multiplying it by an activity factor. This gives you a more complete picture of your daily calorie needs.

Sedentary (little or no exercise): TDEE = RMR × 1.2
Lightly Active (light exercise 1–3 days/week): TDEE = RMR × 1.375
Moderately Active (moderate exercise 3–5 days/week): TDEE = RMR × 1.55
Very Active (hard exercise 6–7 days/week): TDEE = RMR × 1.725
Extra Active (very hard daily exercise): TDEE = RMR × 1.9

For our example, if the moderately active woman (RMR = 1,375 kcal) is moderately active:

TDEE = 1,375 × 1.55 ≈ 2,131 kcal per day.

Factors That Influence Your Resting Energy Use

Your RMR is not static; it is influenced by a number of factors, some within your control and others that are not.

Body Composition: A higher percentage of lean muscle mass results in a higher RMR, as muscle tissue burns more calories at rest than fat tissue.
Age: RMR naturally declines with age, typically by about 2-3% per decade after adulthood, largely due to a loss of lean muscle mass.
Sex: Men generally have a higher RMR than women, primarily because they typically have more muscle mass and different hormone levels.
Genetics: Your genetic makeup plays a role in determining your metabolism's efficiency.
Hormones: Endocrine disorders, such as hyperthyroidism or hypothyroidism, can significantly increase or decrease metabolic rate.
Environmental Temperature: Exposure to cold can increase RMR as your body works harder to maintain a stable core temperature.
Sleep: Poor quality or insufficient sleep can negatively impact hormonal balance, which can affect your metabolic rate.
Diet: Severe calorie restriction can cause your RMR to decrease as your body attempts to conserve energy, a process known as adaptive thermogenesis.

RMR Measurement Methods: Estimation vs. Clinical Testing


Method	How it Works	Accuracy	Advantages	Disadvantages
Predictive Equations (e.g., Mifflin-St Jeor)	Uses your weight, height, age, and sex to estimate RMR based on population averages.	Reasonably accurate for most healthy individuals, but can be less precise for those with unusual body compositions (e.g., highly muscular or very low body fat).	Easily accessible with no special equipment needed; quick to perform.	Less accurate for individuals at weight extremes or with certain health conditions.
Indirect Calorimetry	Measures your oxygen consumption ($VO_2$) and carbon dioxide production ($VCO_2$) to determine energy production.	The gold standard for measuring RMR, providing a highly accurate reading based on your body's exact metabolic processes.	Very accurate and detailed, showing how your body uses energy.	Requires specialized equipment (a metabolic cart) and a trained professional; more expensive and less practical for general use.

How to Influence Your Resting Energy Use

While genetics and age play roles, there are actionable steps you can take to positively influence your RMR:

Build Lean Muscle Mass: Muscle tissue is more metabolically active than fat tissue. Engaging in regular strength and resistance training can increase your muscle mass and, consequently, your RMR.
Stay Hydrated: Your body's metabolic processes require water to function efficiently. Even mild dehydration can slow down your metabolism.
Get Quality Sleep: Adequate, restful sleep is vital for regulating the hormones that control your metabolism. Lack of sleep can disrupt this balance.
Eat Enough Protein: The thermic effect of food (TEF) is the energy your body uses to digest food. Protein has a higher TEF than carbohydrates or fats, meaning your body burns more calories processing it.
Avoid Extreme Calorie Restriction: Drastically cutting calories can trigger a protective response in your body, causing your metabolism to slow down to conserve energy. For sustainable weight management, focus on a moderate, consistent caloric deficit.

Conclusion

Understanding what your resting energy use, or RMR, is provides a valuable foundation for any health or fitness goal. It is not a fixed number but a dynamic figure influenced by lifestyle choices like diet and exercise, as well as factors like age and genetics. By using predictive equations, you can get a solid estimate of your baseline caloric needs, which can then be adjusted based on your activity levels to determine your TDEE. For anyone serious about effective and sustainable weight management, building lean muscle mass and maintaining healthy habits like proper hydration and quality sleep are key to supporting a healthy metabolism.

For more information on the Mifflin-St Jeor equation and its accuracy, consult resources like the National Academy of Sports Medicine (NASM) blog.

Frequently Asked Questions

Basal Metabolic Rate (BMR) and Resting Metabolic Rate (RMR) are often used interchangeably, but BMR is a more controlled measurement taken under strict laboratory conditions (after 12 hours of fasting and 8 hours of sleep). RMR is a less restrictive, more practical measure of your energy use at rest under normal, daily conditions.

The most effective way to increase your resting energy use is by building lean muscle mass through strength and resistance training. Muscle tissue burns more calories at rest than fat tissue, giving your metabolism a long-term boost.

Yes, your diet significantly impacts your RMR. Consuming enough calories prevents your metabolism from slowing down due to starvation mode. Also, eating protein has a higher thermic effect than fat or carbs, meaning your body burns more energy digesting it.

Online calculators that use equations like the Mifflin-St Jeor formula provide a reliable estimate for most people. However, for a truly accurate reading, especially for individuals at weight extremes, a clinical test like indirect calorimetry is necessary.

Your resting energy use naturally declines with age, largely due to a gradual loss of lean muscle mass. This is why it often becomes necessary to reduce calorie intake or increase activity to maintain a healthy weight as you get older.

No, it is not recommended to eat fewer calories than your estimated RMR. This is the minimum energy your body needs to function, and consuming below this level can slow your metabolism, cause fatigue, and lead to negative health effects.

Hormones from the thyroid gland, for example, play a major role in regulating metabolism. Conditions like hypothyroidism (underactive thyroid) can decrease RMR, while hyperthyroidism (overactive thyroid) can increase it.