How many calories does your body burn if you stayed in bed all day? That is your basal metabolic rate — the energy your body needs to keep your organs running, regulate your temperature and maintain your cells. It is the foundation of every calorie requirement calculation, and simpler to work out than most people expect.
Key takeaways
- Your basal metabolic rate (BMR) is the number of calories your body burns at complete rest — with no activity whatsoever.
- The Mifflin-St Jeor formula is the most accurate method for most people: within 10 percent of the measured value for 82 percent of individuals.
- BMR is just the starting point. Your total daily energy expenditure (TDEE) is your BMR multiplied by an activity factor.
- Muscle mass raises your BMR: muscle tissue burns more calories at rest than fat tissue.
- Moveno calculates your TDEE automatically based on your profile — so you have a personalised calorie target from day one.
What is basal metabolic rate?
Your basal metabolic rate (BMR) represents the minimum energy your body needs to stay alive. That includes your heartbeat, breathing, kidney function, cell renewal, hormone production and body temperature regulation.
For most people, BMR accounts for 60 to 75 percent of total daily energy expenditure. That makes it by far the largest component — larger than exercise or any other daily activity.
The Mifflin-St Jeor formula: the most accurate method
Several formulas exist to estimate BMR. In 2005, the American Dietetic Association compared four widely used formulas (Harris-Benedict, Mifflin-St Jeor, Owen and WHO). Result: the Mifflin-St Jeor formula, developed in 1990, performs best — for 82 percent of people, the estimate is within 10 percent of the measured value.
Mifflin-St Jeor formula:
For men: BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age in years) + 5
For women: BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age in years) - 161
Example calculation: A woman aged 30, weighing 65 kg, height 170 cm: BMR = (10 x 65) + (6.25 x 170) - (5 x 30) - 161 BMR = 650 + 1,062.5 - 150 - 161 = 1,401.5 kcal per day
A man aged 35, weighing 80 kg, height 180 cm: BMR = (10 x 80) + (6.25 x 180) - (5 x 35) + 5 BMR = 800 + 1,125 - 175 + 5 = 1,755 kcal per day
From BMR to TDEE: the activity factor
Your BMR is the minimum. Your total daily energy expenditure (TDEE) is calculated by multiplying your BMR by an activity factor (PAL value — Physical Activity Level).
The WHO and FAO define the following categories:
| Activity level | Description | PAL factor |
|---|---|---|
| Sedentary | Little or no movement, desk job | 1.40 to 1.55 |
| Lightly active | Light movement 1 to 3 days per week | 1.55 to 1.70 |
| Moderately active | Moderate movement 3 to 5 days per week | 1.70 to 1.85 |
| Active | Intensive movement 6 to 7 days per week | 1.85 to 2.00 |
| Very active | Heavy physical labour or competitive sport | 2.00 to 2.40 |
For the woman in the example above, who is lightly active (PAL 1.60): TDEE = 1,401.5 x 1.60 = 2,242 kcal per day
What influences your BMR?
Muscle mass
Muscle tissue burns significantly more calories at rest than fat tissue. Strength training increases muscle mass and therefore raises your BMR — one of the reasons resistance training is effective for long-term weight management.
Age
After your thirties, BMR declines by an average of 1 to 2 percent per decade, partly due to the gradual loss of muscle mass (sarcopenia). Staying active and eating adequate protein can partially offset this decline.
Sex
Men typically have a higher BMR than women of the same weight and height, primarily due to a higher proportion of muscle mass. The Mifflin-St Jeor formula corrects for this via the constants (+5 for men, -161 for women).
Body composition
Two people of the same weight can have very different BMRs depending on their body fat percentage. Someone with more muscle mass burns more at rest than someone with more fat mass at the same weight.
Thyroid function
The thyroid gland regulates metabolism. An underactive thyroid (hypothyroidism) lowers BMR; an overactive thyroid raises it. If you suspect a thyroid issue, a blood test through your GP is the appropriate next step.
BMR vs. BMI: what is the difference?
BMI (Body Mass Index) is a rough ratio of weight to height that says nothing about energy expenditure or body composition. BMR is an estimate of your energy requirement at rest. They measure fundamentally different things.
For calorie and nutrition planning, BMR is far more useful than BMI. BMI does not tell you how many calories you need — BMR (and TDEE) does.
How to use your BMR in practice
Once you know your TDEE, you have a reference point:
- Maintain weight: eat roughly equal to your TDEE.
- Lose weight: eat 300 to 500 kcal per day less than your TDEE for a gradual, sustainable pace.
- Build muscle: eat 200 to 300 kcal per day more than your TDEE.
Want to learn more about calorie tracking for weight management? Read our calorie tracking beginner's guide, learn to calculate your calorie deficit, and check how to calculate macros for weight loss. Also see how much daily protein you need to preserve muscle.
When you set up Moveno, you enter your weight, height, age, sex and activity level. The app calculates your TDEE automatically and sets a personalised calorie target — so you can focus on eating, not calculating.
Start defining your calorie target today
Your BMR is the key to a realistic calorie requirement. Calculate it now using the formula above, multiply by your activity factor, and you have a solid starting point.
Want to track this without doing the maths? Create an account in Moveno and let the app handle the calculation for you.
Sources
- Evidencio — Basaalmetabolisme Mifflin formula — validation of the Mifflin-St Jeor formula for BMR calculation
- Fitsome — Basal Metabolic Rate berekenen — Mifflin-St Jeor formula explained with scientific background
- WHO — Healthy diet — WHO energy and activity level definitions
- Voedingscentrum — Energiebehoefte — Dutch guidelines for daily energy requirements
