Resting Metabolic Rate Calculator (UK)
Your Results
Your estimated Resting Metabolic Rate is:
This is the number of calories your body burns at complete rest.
| Activity Level | Calories/Day |
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Understanding Your Resting Metabolic Rate in the UK
Whether you are embarking on a weight loss journey, looking to gain muscle mass, or simply aiming to maintain a healthy lifestyle, understanding your energy expenditure is fundamental. Our Resting Metabolic Rate (RMR) Calculator UK uses scientifically validated formulas to estimate the number of calories your body requires to function at rest.
What is Resting Metabolic Rate (RMR)?
Resting Metabolic Rate represents the energy (measured in calories or kilocalories/kcal) your body burns to perform basic life-sustaining functions while you are at rest. These functions include breathing, circulating blood, controlling body temperature, and cell growth.
In the UK, nutritional information is typically provided in kcal (often just referred to as "calories"). Your RMR accounts for approximately 60% to 75% of the total calories you burn each day. It does not include calories burned through digestion (Thermic Effect of Food) or physical activity.
How is RMR Calculated?
This calculator utilises the Mifflin-St Jeor equation, which is widely considered by the NHS and dietetic associations globally to be one of the most accurate methods for estimating RMR in healthy individuals without using expensive laboratory equipment (like indirect calorimetry).
The formula takes into account four key variables:
- Weight: Heavier bodies require more energy to function.
- Height: Taller individuals typically have a larger body surface area, increasing metabolic rate.
- Age: As we age, our metabolic rate naturally slows down, often due to a decrease in muscle mass.
- Gender: Men generally have a higher RMR than women due to higher lean muscle mass.
RMR vs. BMR: What is the Difference?
You may often see the terms RMR and BMR (Basal Metabolic Rate) used interchangeably. While they are very similar, there is a technical distinction:
- BMR (Basal Metabolic Rate): The absolute minimum energy required for survival, measured under very strict clinical conditions (usually after 8 hours of sleep and 12 hours of fasting, in a darkened room).
- RMR (Resting Metabolic Rate): Also measures resting energy expenditure but under less strict conditions. It is a more practical figure for everyday weight management.
For most practical purposes in the UK, the two numbers are close enough that RMR is the standard metric used for dietary planning.
How to Use This Information for Weight Management
Calculating your RMR is step one. To understand your total daily calorie needs, you must account for your activity level. This is known as your Total Daily Energy Expenditure (TDEE).
The calculator above provides your TDEE based on standard activity multipliers:
- Sedentary: RMR x 1.2 (Little to no exercise, desk job)
- Lightly Active: RMR x 1.375 (Light exercise/sports 1-3 days/week)
- Moderately Active: RMR x 1.55 (Moderate exercise/sports 3-5 days/week)
- Very Active: RMR x 1.725 (Hard exercise/sports 6-7 days/week)
To lose weight: A common guideline suggests creating a calorie deficit. For example, consuming 500 kcal less than your TDEE per day generally results in a weight loss of approximately 0.5kg per week.
To gain weight: You would aim to consume more than your TDEE, combined with resistance training to promote muscle growth rather than just fat storage.
Factors That Influence Your RMR
While the calculator provides an accurate estimate, individual RMR can vary due to:
- Muscle Mass: Muscle tissue burns more calories at rest than fat tissue. Increasing muscle mass through strength training is one of the best ways to boost your RMR.
- Genetics: Some people naturally have a faster or slower metabolism.
- Hormones: Thyroid issues (hypothyroidism or hyperthyroidism) can significantly alter metabolic rate.
- Environment: Extreme cold or heat forces the body to work harder to maintain internal temperature.
Disclaimer: This calculator is for informational purposes only and does not constitute medical advice. Always consult a GP or registered dietitian in the UK before making significant changes to your diet or exercise programme.