How to Use BMR Calculator
The BMR Calculator estimates the number of calories your body needs to maintain basic life functions — breathing, circulation, and cell production — at complete rest.
- Select your unit system — Choose Metric (kg / cm) or Imperial (lbs / ft + in) using the toggle at the top of the BMR Calculator.
- Choose your biological sex — Male and female have different constants in the Mifflin-St Jeor formula used by the BMR Calculator.
- Enter your age — Input your age in years. The BMR Calculator supports ages from 1 to 120.
- Enter your weight and height — Fill in the fields for your weight and height. For imperial, enter feet and inches separately.
- Read your result — The BMR Calculator instantly displays your Basal Metabolic Rate in kcal/day, along with TDEE estimates for five common activity levels.
No button press is needed — the BMR Calculator updates in real time as you type.
Formula & Theory — BMR Calculator
The BMR Calculator uses the Mifflin-St Jeor equation, published in 1990 and widely regarded as the most accurate BMR formula for healthy adults:
Male: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5
Female: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161
| Symbol | Meaning |
|---|---|
| weight | Body weight in kilograms |
| height | Height in centimetres |
| age | Age in years |
When you select imperial units, the BMR Calculator converts pounds to kilograms (× 0.4536) and feet/inches to centimetres before applying the formula, so the result is always accurate.
Activity Level Multipliers (TDEE)
The BMR Calculator also shows TDEE estimates by multiplying BMR by standard activity factors defined by the Harris-Benedict revision:
| Activity Level | Multiplier |
|---|---|
| Sedentary | × 1.20 |
| Lightly Active (1–3 days/week) | × 1.375 |
| Moderately Active (3–5 days/week) | × 1.55 |
| Very Active (6–7 days/week) | × 1.725 |
| Extra Active (hard daily exercise) | × 1.90 |
Use Cases for BMR Calculator
The BMR Calculator is a practical starting point for a wide range of health and fitness goals:
- Weight management — Knowing your BMR gives you a caloric floor: eating below it for extended periods can impair metabolism and lean mass.
- Diet planning — Nutritionists use the BMR Calculator to set minimum calorie thresholds before designing meal plans for clients.
- Fitness goal setting — Athletes use BMR alongside training logs to calculate total daily needs and ensure adequate fuelling for performance.
- Medical and clinical use — Healthcare professionals use basal metabolic rate estimates to guide nutritional support for post-operative or critically ill patients.
- Health awareness — Even without a fitness goal, running the BMR Calculator gives you a concrete, personalised number that makes abstract nutrition advice tangible.
Understanding your basal metabolic rate through the BMR Calculator is the foundation for any informed calorie management strategy, whether you aim to lose fat, build muscle, or simply maintain your current weight.