BMR Calculator: Basal Metabolic Rate

Your Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest over 24 hours. It covers basic functions like breathing, circulation, and cell repair. BMR typically accounts for 60–75% of your total calorie burn. Knowing it helps you plan your diet more accurately than generic advice.

• Diet planning baseline: BMR is the floor for calorie intake. Eating below BMR long-term is generally unsafe without medical oversight.
• Understanding metabolism: Compare BMR across ages to see how metabolism slows over time. The typical decline is roughly 1 to 2% per decade after age 30.
• Fitness coaching: Coaches use client BMR as a foundation for building calorie targets that support performance and body composition goals.
• Medical nutrition therapy: Dietitians use BMR estimates to set calorie targets for patients recovering from illness or surgery.

1. 1Enter your weight in kilograms, height in centimeters, and age.
2. 2Select your gender. The Mifflin-St Jeor formula uses a different constant for men and women.
3. 3The calculator applies the formula and outputs your BMR in kilocalories per day.
4. 4Estimated TDEE values for sedentary and lightly active lifestyles are shown for reference.
5. 5For a full TDEE with all activity levels, use the Calorie Calculator.

• Using BMR as your actual calorie target: BMR is the calories you burn at rest with zero activity. Eating at BMR while living your normal life will put you in a deficit. Multiply BMR by an activity factor to get your maintenance calories.
• Entering weight without adjusting for unit: Make sure your weight is in kilograms, not pounds, if the calculator expects metric. 70 kg and 70 lb differ by over 38 kg. A unit error here throws off the entire result.
• Assuming BMR does not change: BMR changes as you age, gain or lose weight, and as your body composition shifts. Recalculate every few months if you are actively tracking diet or fitness.
• Choosing the wrong formula: The Mifflin-St Jeor equation is more accurate than the older Harris-Benedict formula for most adults. If another tool gives you a different number, it may be using a different equation.

• Use BMR as the starting point, not the end point: BMR tells you your floor. Multiply it by 1.2 (sedentary) to 1.9 (very active) to get your TDEE. That is the number you adjust up or down from to lose, gain, or maintain weight.
• Weigh yourself at the same time each day: Morning weight after using the bathroom is the most consistent measurement. Daily fluctuations of 1-2 kg are normal due to water retention. Use a weekly average rather than daily readings.
• Recalculate after significant weight change: For every 5 kg of weight change, your BMR shifts meaningfully. People who lose weight often stall because they kept the same calorie target while their BMR dropped.
• Combine with body fat data for lean mass BMR: Standard BMR formulas do not distinguish between muscle and fat. If you know your body fat percentage, the Katch-McArdle formula (based on lean body mass) may be more accurate for athletes.