How To Calculate My Resting Metabolic Rate

Calculate your body's baseline calorie expenditure.

RMR Calculator

Calculation Details

The Mifflin-St Jeor Equation is commonly used:
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

What is Resting Metabolic Rate (RMR)?

Resting Metabolic Rate (RMR) is the total number of calories your body burns to maintain basic, life-sustaining functions while at rest. This includes functions like breathing, circulation, cell production, and nutrient processing. Essentially, it's the energy your body requires to keep running if you were to do nothing but rest for 24 hours.

Understanding your RMR is crucial for managing your weight and overall health. It forms the largest component of your Total Daily Energy Expenditure (TDEE), which is the total number of calories you burn in a day. By knowing your RMR, you can better estimate your calorie needs for weight loss, maintenance, or gain.

Who should use an RMR calculator? Anyone interested in:

• Weight management (losing, gaining, or maintaining weight)
• Optimizing fitness and nutrition plans
• Understanding their body's energy needs
• Assessing the impact of age or lifestyle changes on metabolism

Common misunderstandings about RMR often revolve around its constancy. While RMR is relatively stable for an individual, it's not fixed. Factors like muscle mass, age, and hormonal changes can influence it. Furthermore, RMR is often confused with Basal Metabolic Rate (BMR), which is measured under even stricter conditions and is slightly lower than RMR. Our calculator uses the Mifflin-St Jeor equation, which is widely accepted for estimating RMR in practical settings.

RMR Formula and Explanation

The most commonly used and validated formula for estimating Resting Metabolic Rate is the Mifflin-St Jeor Equation. It takes into account biological sex, age, weight, and height to provide an estimate.

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

Variable Explanations:

Variables Used in the Mifflin-St Jeor Equation

Variable	Meaning	Unit (Input)	Typical Range
Weight	Body mass	Kilograms (kg) or Pounds (lbs)	30 – 200+ kg / 66 – 440+ lbs
Height	Body length	Centimeters (cm), Inches (in), or Feet/Inches	140 – 200+ cm / 55 – 80+ in
Age	Years since birth	Years	18 – 90+ years
Sex	Biological sex	Male / Female	N/A
RMR	Resting Metabolic Rate	Calories per day (kcal/day)	1200 – 2500+ kcal/day

Practical Examples

Let's see how the RMR calculator works with real-world examples.

Example 1: Sarah, a Moderately Active Woman

Inputs:

• Biological Sex: Female
• Age: 35 years
• Weight: 65 kg
• Height: 168 cm
• Activity Level: Moderately Active

Calculation:
RMR = (10 × 65) + (6.25 × 168) – (5 × 35) – 161
RMR = 650 + 1050 – 175 – 161
RMR = 1364 kcal/day
Estimated RMR: 1364 kcal/day
Total Daily Energy Expenditure (TDEE) for Moderately Active = RMR × 1.55 = 2114 kcal/day

Example 2: John, a Sedentary Man

Inputs:

• Biological Sex: Male
• Age: 50 years
• Weight: 88 kg
• Height: 180 cm
• Activity Level: Sedentary

Calculation:
RMR = (10 × 88) + (6.25 × 180) – (5 × 50) + 5
RMR = 880 + 1125 – 250 + 5
RMR = 1760 kcal/day
Estimated RMR: 1760 kcal/day
Total Daily Energy Expenditure (TDEE) for Sedentary = RMR × 1.20 = 2112 kcal/day

Unit Conversion Impact

If John's weight was entered as 194 lbs (88 kg converted), the calculator would handle the conversion internally. Using the formula with pounds directly would require a different equation. Our calculator ensures consistency by converting all inputs to metric units (kg and cm) for the calculation, regardless of the input unit selected.

How to Use This RMR Calculator

1. Select Biological Sex: Choose 'Male' or 'Female' from the dropdown. This is a key factor in metabolic rate estimations.
2. Enter Age: Input your age in years. Metabolism tends to slow down with age.
3. Enter Weight: Input your current weight. You can choose between Kilograms (kg) or Pounds (lbs). The calculator will convert lbs to kg internally.
4. Enter Height: Input your height. You can select Centimeters (cm), Inches (in), or Feet & Inches. If you choose Feet & Inches, use the separate fields provided. The calculator converts all height inputs to centimeters internally.
5. Select Activity Level: Choose the option that best describes your average weekly physical activity. This helps estimate your Total Daily Energy Expenditure (TDEE) which builds upon your RMR.
6. Click 'Calculate RMR': The calculator will display your estimated RMR in kilocalories per day (kcal/day).
7. Review Intermediate Results: See the breakdown of how your inputs contribute to the final RMR.
8. Use the 'Copy Results' Button: Easily copy your calculated RMR, units, and the formula used for your records or to share.
9. Reset: Click 'Reset' to clear all fields and return to default values.

Interpreting Results: Your RMR is the baseline calorie burn. To lose weight, you generally need to consume fewer calories than your TDEE. To gain weight, consume more. Your TDEE is RMR multiplied by an activity factor (provided by the calculator). Remember, these are estimates; individual metabolism can vary.

Key Factors That Affect Resting Metabolic Rate

1. Body Composition (Muscle vs. Fat Mass): Muscle tissue is metabolically more active than fat tissue. Individuals with higher muscle mass have a higher RMR, even at the same body weight. Losing fat and gaining muscle can increase your RMR.
2. Age: Metabolic rate generally declines with age, often starting in the late 20s or early 30s. This is partly due to natural muscle loss (sarcopenia) and hormonal changes.
3. Sex: On average, men tend to have a higher RMR than women. This is primarily due to differences in body composition (men typically have more muscle mass) and hormonal profiles.
4. Genetics: Your inherited genes play a significant role in determining your metabolic rate. Some individuals naturally have a faster or slower metabolism.
5. Hormones: Thyroid hormones (T3 and T4) are major regulators of metabolism. Imbalances, such as hypothyroidism (underactive thyroid) or hyperthyroidism (overactive thyroid), can significantly alter RMR.
6. Environmental Temperature: Your body expends energy to maintain its core temperature. In very cold environments, RMR might slightly increase as your body works harder to stay warm (thermogenesis). In very hot environments, it can also increase due to the energy cost of sweating and cooling.
7. Dietary Intake: Severe calorie restriction over long periods can lead to a decrease in RMR as the body adapts to conserve energy. Conversely, the thermic effect of food (TEF) – the calories burned during digestion – contributes slightly to TDEE but doesn't directly impact RMR itself.

Frequently Asked Questions (FAQ)

What's the difference between RMR and BMR?

BMR (Basal Metabolic Rate) is measured under very specific conditions (e.g., after an overnight fast, in a dark, temperature-controlled room, lying still). RMR (Resting Metabolic Rate) is a more practical estimate of calories burned at rest throughout the day and can be slightly higher than BMR. Our calculator estimates RMR using a widely accepted formula.

How accurate is the Mifflin-St Jeor equation?

The Mifflin-St Jeor equation is considered one of the most accurate predictive equations for RMR in the general adult population, especially compared to older formulas like Harris-Benedict. However, it's still an estimate, and individual variations exist.

Why do men generally have a higher RMR?

Men typically have a higher proportion of muscle mass compared to women, and muscle tissue burns more calories at rest than fat tissue. Hormonal differences also play a role.

Can my RMR change over time?

Yes, your RMR can change. Factors like significant weight loss or gain, changes in body composition (muscle vs. fat), aging, and certain medical conditions (like thyroid disorders) can affect your metabolic rate.

How does activity level affect my calorie needs?

While activity level doesn't directly change your RMR (calories burned at rest), it significantly increases your Total Daily Energy Expenditure (TDEE). Your TDEE = RMR + calories burned through physical activity. The calculator uses activity level to estimate TDEE.

What does it mean if my RMR is considered 'low'?

A lower RMR means your body burns fewer calories at rest. If your calorie intake exceeds your TDEE (which is based on your RMR and activity level), you're more likely to gain weight. Conversely, if you have a higher RMR, you might find it easier to maintain weight or lose it.

Should I worry about the units (kg vs lbs, cm vs inches)?

No, our calculator handles unit conversions automatically. Just ensure you select the correct unit for your input (kg or lbs, cm or inches), and the tool will convert it to the metric units required for the calculation internally. The result will be displayed in kcal/day.

Can I calculate RMR for children?

The Mifflin-St Jeor equation is validated for adults (typically 18+ years). For children and adolescents, different formulas or pediatric growth charts are typically used by healthcare professionals. This calculator is intended for adult use.

What is the calorie unit used for RMR?

RMR is almost universally expressed in kilocalories per day (kcal/day). Sometimes referred to simply as 'calories'.