BMR (Basal Metabolic Rate) Calculator

How to Use This Tool

Follow these steps to calculate your BMR and related metrics:

• Select your gender from the dropdown menu.
• Enter your age in years (must be between 15 and 100).
• Input your weight and select the appropriate unit (kg or lbs).
• Input your height and select the appropriate unit (cm or inches).
• Choose your preferred BMR formula: Mifflin-St Jeor (recommended for accuracy) or Harris-Benedict (traditional).
• Select your typical activity level from the dropdown.
• Click the Calculate BMR button to see your results.
• Use the Reset button to clear all inputs and start over.
• Click Copy Results to save your metrics to your clipboard.

Formula and Logic

This tool uses two widely accepted BMR formulas, with all calculations converted to metric units (kg, cm) internally for consistency:

Mifflin-St Jeor Formula (Recommended)

For males: BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age) + 5

For females: BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age) - 161

Harris-Benedict Formula

For males: BMR = 66.5 + (13.75 × weight in kg) + (5.003 × height in cm) - (6.755 × age)

For females: BMR = 655.1 + (9.563 × weight in kg) + (1.850 × height in cm) - (4.676 × age)

Total Daily Energy Expenditure (TDEE) is calculated by multiplying BMR by the activity level multiplier selected. Weight loss and gain targets are derived by applying a 20% deficit or surplus to your TDEE, respectively.

Practical Notes

Keep these health-specific considerations in mind when using your results:

• BMR is an estimate: Individual metabolic rates vary based on genetics, muscle mass, thyroid function, and other health factors. These calculations provide a baseline, not an exact measurement.
• Consult a professional: If you have underlying health conditions, are pregnant, or are planning major dietary changes, consult a doctor or registered dietitian before adjusting your calorie intake.
• Muscle mass impact: Higher muscle mass increases BMR, as muscle tissue burns more calories at rest than fat tissue. Strength training can gradually raise your BMR over time.
• Activity level accuracy: TDEE estimates depend on your selected activity level. Be honest about your typical routine—overestimating activity can lead to inaccurate calorie targets.
• Dietary guidelines: Gradual weight loss (0.5-1 kg per week) is safer and more sustainable than extreme calorie restriction. Do not drop below 1200 calories/day for females or 1500 calories/day for males without medical supervision.

Why This Tool Is Useful

This calculator serves a wide range of health and fitness goals:

• Fitness enthusiasts can align their calorie intake with training demands to support muscle gain or fat loss.
• Dietitians can use it to create personalized nutrition plans for clients without manual calculations.
• Endurance athletes can adjust their calorie targets based on training volume and activity levels.
• Health-conscious individuals can maintain a healthy weight by matching their intake to their daily energy expenditure.
• The inclusion of two formula options and unit conversions makes it accessible to users worldwide, regardless of preferred measurement systems.

Frequently Asked Questions

Is BMR the same as the number of calories I should eat every day?

No. BMR measures calories burned at complete rest. Most people need to eat more than their BMR to support daily activity, digestion, and exercise. TDEE, which accounts for activity, is a better baseline for daily calorie targets.

Why does the Mifflin-St Jeor formula give a different result than Harris-Benedict?

The Mifflin-St Jeor formula was developed using more recent population data and is widely considered more accurate for modern adults. The Harris-Benedict formula, created in 1919, tends to overestimate BMR for some groups.

Can I use this tool if I am pregnant or breastfeeding?

These formulas do not account for the increased calorie needs of pregnancy or breastfeeding. Consult your doctor or a prenatal dietitian for appropriate calorie targets during these periods.

Additional Guidance

To get the most out of your BMR results:

• Recalculate every 3-6 months: Weight changes, aging, and shifts in muscle mass will alter your BMR over time.
• Track your intake: Use a food diary to compare your actual calorie consumption to your target, and adjust as needed based on progress.
• Pair with activity tracking: If your exercise routine changes (e.g., starting a new training program), update your activity level selection to get accurate TDEE estimates.
• Avoid crash dieting: Severe calorie restriction can lower your BMR as your body adapts to conserve energy, making long-term weight management harder.