BMR Calculator
The BMR Calculator estimates your Basal Metabolic Rate using the Mifflin-St Jeor equation. BMR is the number of calories your body burns at rest.
BMR Calculator
What the result means
BMR represents the minimum energy your body needs to function at rest. Your total daily energy expenditure (TDEE) is higher because it includes physical activity.
How to use this calculator
- 1Select your sex.
- 2Enter your weight, height and age.
- 3Press Calculate to see your BMR.
The formula
The calculation uses a standard, verifiable formula. Here it is in its simplest form.
What each variable means
| Symbol | Name | Description |
|---|---|---|
| W | Weight | Weight in kilograms. |
| H | Height | Height in centimeters. |
| A | Age | Age in years. |
Step-by-step example
Example: Male, 70kg, 175cm, 30 years
- 1BMR = 10(70) + 6.25(175) − 5(30) + 5
- 2BMR = 700 + 1093.75 − 150 + 5
- 3BMR = 1648.75
Result
BMR ≈ 1,649 calories/day
What changes the result
- Muscle mass increases BMR.
- Age affects BMR (it decreases with age).
- The equation is most accurate for average body compositions.
Edge cases to be aware of
Unusual situations handled correctly
- Very muscular individuals may have higher BMR than estimated.
- The formula is less accurate for extreme body types.
Common mistakes
Avoid these errors
- Using BMR as your total daily calories (it excludes activity).
- Entering height in meters instead of centimeters.
Assumptions
- Average body composition.
- Standard metabolic conditions.
Limitations
- This is an estimate, not a medical measurement.
- Individual BMR can vary by 10-15%.
Key terms to know
Basal Metabolic Rate (BMR)+
Total Daily Energy Expenditure (TDEE)+
Mifflin-St Jeor equation+
Resting energy expenditure+
Activity factor+
Energy balance+
Real-world scenarios
Two people, same weight, different BMR
A 30-year-old male and a 30-year-old female both weigh 70 kg and are 175 cm tall.
What it means: The Mifflin-St Jeor equation adds 5 for males and subtracts 161 for females, so the male's BMR is about 166 calories higher. This reflects average differences in body composition, not a personal verdict.
Age and BMR
The same person at 30 and at 60 years old.
What it means: The equation subtracts 5 calories per year of age. This reflects the tendency for muscle mass and metabolic rate to decline with age, though individual variation is large.
BMR vs daily needs
A person's BMR is 1,600 calories, but they are moderately active.
What it means: Their TDEE is roughly 1,600 × 1.55 ≈ 2,480 calories. Using BMR alone as a daily calorie target would understate real needs — BMR is only the resting component.
Muscle mass and BMR
Two people with identical weight, height, and age, but different muscle mass.
What it means: The equation assumes average body composition. A more muscular person typically has a higher true BMR than the estimate, which is why the result is a useful reference rather than an exact measurement.
Related concepts
Daily calorie needs
BMR is the resting component of your daily energy needs. The calorie calculator applies an activity factor to estimate your total daily expenditure.
Body Mass Index
BMI relates weight to height, while BMR estimates resting energy needs. Together they give a broader picture of body size and energy requirements.
Body fat percentage
Body composition influences BMR — more muscle generally means a higher resting burn. A body-fat estimate can help explain why two similar people have different metabolic needs.
Macronutrient targets
Once you know your calorie needs, macro targets help you plan protein, carbohydrate, and fat intake to match your goals.