Basal Metabolic Rate (BMR) Calculator
Estimate your Basal Metabolic Rate (Mifflin–St Jeor) and daily calories by activity level.
Notes: BMR assumes a rested, fasted state in a neutral-temperature environment. Activity factors are estimates; individual needs vary.
How the BMR Calculator Works
The BMR Calculator estimates your Basal Metabolic Rate (BMR) using the Mifflin–St Jeor equation and then projects your approximate daily calorie needs across multiple activity levels. BMR is the energy your body would burn in complete rest—no movement, no digestion, just keeping you alive. From there, activity multipliers are applied to estimate realistic maintenance calories for your lifestyle.
Mifflin–St Jeor Formula (Metric-Based)
All calculations are normalized to metric units (cm, kg) internally, even when you enter US units:
- For men:
BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5 - For women:
BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161
When you use US Units, the calculator converts:
- Height (ft/in) → centimeters
- Weight (lb) → kilograms
That converted data is then passed through the same Mifflin–St Jeor formula, ensuring consistent results regardless of input mode.
Activity Levels & Maintenance Calories
To estimate daily calorie needs (TDEE-style outputs), the calculator multiplies your BMR by standard activity factors:
- Sedentary (~1.2): little or no exercise.
- Light (~1.375): light exercise 1–3 days/week.
- Moderate (~1.55): moderate exercise 3–5 days/week.
- High (~1.725): hard exercise or physical job.
- Very High (~1.9): intense training or very active work.
Each row in the results table shows an estimated maintenance calories per day for that activity level, formatted for readability so you can quickly compare options.
Input Validation & Realistic Ranges
To keep outputs meaningful, the calculator:
- Restricts age, height, and weight to realistic adult ranges.
- Requires sex selection to apply the correct version of the Mifflin–St Jeor formula.
- Displays dashes instead of values when inputs are incomplete or invalid.
These checks help prevent obviously wrong results from typos or missing data, which is important for both user trust and SEO quality.
Practical Use Cases
This BMR Calculator is ideal for:
- Estimating a starting point for weight maintenance, loss, or gain plans.
- Comparing different activity levels to see how lifestyle changes affect calorie needs.
- Educating clients or students on the difference between BMR and daily expenditure.
What This Tool Doesn't Do
While useful, this calculator has intentional limits:
- It does not account for body fat percentage, lean mass, genetics, medications, hormones, or health conditions.
- It does not adapt dynamically to metabolic changes from long-term dieting or training.
- It does not provide medical, dietary, or clinical advice.
Educational Insight
Think of your BMR as the foundation of your energy budget. By combining a science-backed equation with clear activity multipliers, this BMR Calculator gives you a solid, transparent starting point for understanding your daily calorie needs—something you can refine over time with real-world tracking and professional guidance if needed.