Calculate Resting Metabolic Rate

Determine your baseline daily calorie expenditure.

RMR Calculator

What is Resting Metabolic Rate (RMR)?

Resting Metabolic Rate (RMR) is the minimum amount of energy (calories) your body needs to function at rest. This includes essential physiological processes such as breathing, maintaining body temperature, circulating blood, and cellular repair. It's often considered a more accurate measure of your basal metabolic rate (BMR) under less strict resting conditions. Understanding your RMR is fundamental to managing your weight, optimizing your diet, and supporting your overall health and fitness goals.

Who should use an RMR calculator? Anyone interested in weight management, athletic performance, nutrition planning, or simply understanding their body's energy needs better can benefit from calculating their RMR. It provides a baseline calorie expenditure before any physical activity is factored in.

Common Misunderstandings: A frequent misunderstanding is confusing RMR with total daily energy expenditure (TDEE). RMR is only one component of TDEE; the rest comes from the thermic effect of food and physical activity. Another confusion arises with units: ensuring consistent weight (kg) and height (cm) is vital for accurate RMR calculations, as different formulas are sensitive to these inputs.

RMR Formulas and Explanation

Several formulas estimate RMR, with the Mifflin-St Jeor equation generally considered the most accurate for most people. We've included the widely recognized Harris-Benedict (Revised) formula as well for comparison.

Mifflin-St Jeor Equation:

For Men: RMR = (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) + 5

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

Harris-Benedict (Revised) Equation:

For Men: RMR = (13.397 × weight in kg) + (4.799 × height in cm) – (5.677 × age in years) + 88.362

For Women: RMR = (9.247 × weight in kg) + (3.098 × height in cm) – (4.330 × age in years) + 447.593

The calculator uses these standard formulas. You provide your gender, age, weight, and height, and it outputs your estimated RMR in kilocalories per day (kcal/day).

Variables Table:

RMR Calculation Variables

Variable	Meaning	Unit	Typical Range
Gender	Biological sex	Male / Female	N/A
Age	Years since birth	Years	1 – 120
Weight	Body mass	Kilograms (kg) / Pounds (lb)	1 – 500 kg (2.2 – 1100 lb)
Height	Body length from feet to head	Centimeters (cm) / Inches (in) / Feet & Inches	50 – 250 cm (1.6 – 8.2 ft)
RMR	Resting Metabolic Rate	Kilocalories per day (kcal/day)	800 – 2500+ kcal/day

Practical Examples

Let's illustrate with two individuals:

Example 1: Sarah

Sarah is a 28-year-old female, weighs 65 kg (143.3 lb), and is 168 cm (5'6″) tall.

Using the calculator with these inputs:

• Gender: Female
• Age: 28 years
• Weight: 65 kg
• Height: 168 cm

Estimated RMR (Mifflin-St Jeor): Approximately 1420 kcal/day.

Estimated RMR (Harris-Benedict Revised): Approximately 1475 kcal/day.

Example 2: Mark

Mark is a 35-year-old male, weighs 85 kg (187.4 lb), and is 180 cm (5'11") tall.

Using the calculator with these inputs:

• Gender: Male
• Age: 35 years
• Weight: 85 kg
• Height: 180 cm

Estimated RMR (Mifflin-St Jeor): Approximately 1870 kcal/day.

Estimated RMR (Harris-Benedict Revised): Approximately 1930 kcal/day.

How to Use This RMR Calculator

1. Select Gender: Choose 'Male' or 'Female' based on biological sex.
2. Enter Age: Input your age in whole years.
3. Enter Weight: Input your current weight. Use the dropdown to select your unit (kg or lb). The calculator will convert pounds to kilograms internally for the formulas.
4. Enter Height: Input your height. Select the unit (cm, inches, or feet/inches). If you choose feet/inches, enter the values in the provided fields. The calculator converts all height inputs to centimeters.
5. Calculate: Click the "Calculate RMR" button.
6. Interpret Results: Your RMR will be displayed in kcal/day based on the Mifflin-St Jeor equation, along with the Harris-Benedict (Revised) estimate. The calculator also shows equivalent weight and height values for context.
7. Adjust Units: You can easily switch between units for weight and height and see how the results might be affected.
8. Copy Results: Use the "Copy Results" button to quickly save your calculated RMR and its associated inputs.

Key Factors That Affect Resting Metabolic Rate

1. Body Composition (Muscle Mass): Muscle tissue is metabolically more active than fat tissue. Individuals with higher muscle mass generally have a higher RMR.
2. Age: RMR tends to decrease with age, partly due to a natural decline in muscle mass and hormonal changes.
3. Sex: On average, men tend to have a higher RMR than women, primarily due to differences in body composition (higher muscle mass and lower body fat percentage).
4. Genetics: Your inherited genetic makeup plays a role in determining your metabolic rate. Some individuals naturally have a faster metabolism.
5. Hormonal Factors: Thyroid hormones, in particular, significantly regulate metabolism. Conditions like hypothyroidism (underactive thyroid) can lower RMR, while hyperthyroidism (overactive thyroid) can raise it.
6. Body Size and Surface Area: Larger individuals generally have a higher RMR simply because they have more tissue to maintain.
7. Environmental Temperature: In very cold or very hot environments, your body expends more energy to maintain its core temperature, potentially increasing RMR slightly.
8. Diet and Caloric Intake: Severe calorie restriction can lead to a decrease in RMR as the body adapts to conserve energy.

FAQ about RMR Calculation

Q1: What's the difference between RMR and BMR?

A1: RMR (Resting Metabolic Rate) and BMR (Basal Metabolic Rate) are often used interchangeably. BMR is measured under very strict conditions (lying down, awake, fasting, in a neutral temperature environment). RMR is a less strict measurement, taken after a short rest period, and is generally slightly higher than BMR. For practical purposes, RMR is often a more accessible and still highly useful measure.

Q2: Is RMR the same as TDEE?

A2: No. RMR is the calories burned at rest. TDEE (Total Daily Energy Expenditure) includes RMR, plus the calories burned through digesting food (Thermic Effect of Food) and physical activity (exercise and non-exercise activity thermogenesis). TDEE is a more comprehensive measure of daily calorie needs.

Q3: How accurate are these RMR formulas?

A3: RMR formulas provide estimates. The Mifflin-St Jeor equation is considered more accurate for the general population than the older Harris-Benedict equation. However, individual metabolic rates can vary due to genetics, body composition, and other factors not captured by these formulas. For precise measurements, a clinical assessment like indirect calorimetry might be needed.

Q4: What if I have a medical condition affecting my metabolism?

A4: If you have conditions like thyroid disorders, diabetes, or are on certain medications, these formulas might not be accurate. Consult a healthcare professional or a registered dietitian for personalized advice and potentially more accurate metabolic assessments.

Q5: How do I convert pounds to kilograms or inches to centimeters?

A5: 1 pound (lb) is approximately 0.453592 kilograms (kg). 1 inch (in) is approximately 2.54 centimeters (cm). Our calculator handles these conversions automatically when you select your preferred units.

Q6: Can RMR change over time?

A6: Yes, RMR can change. Factors like significant weight loss or gain, increased muscle mass through exercise, aging, and changes in hormonal balance can all influence your RMR.

Q7: Why does the calculator show two different RMR values?

A7: The calculator provides estimates from two common formulas (Mifflin-St Jeor and Harris-Benedict Revised) to give you a broader perspective. The Mifflin-St Jeor is generally preferred for its higher accuracy in modern populations.

Q8: What are "intermediate results" like weight and height equivalents?

A8: These are provided for context. The 'Weight Equivalent' shows how much lean mass you might have if your RMR corresponded to a standard metabolic rate per kg of body weight. The 'Height Equivalent' is a calculated value based on your weight and gender, not a direct measure of your height. They are not primary outputs for TDEE calculation but offer additional data points.