BMR Calculator — Basal Metabolic Rate
This calculator provides estimates for educational purposes only and is not medical advice. Results may vary based on individual factors. Consult a healthcare provider before making changes to your diet or exercise routine.
What is Basal Metabolic Rate (BMR)?
Your Basal Metabolic Rate is the number of calories your body needs just to survive at complete rest. Think of it as the energy cost of being alive — your heart beating, lungs breathing, brain thinking, and cells regenerating. Even if you stayed in bed all day doing absolutely nothing, your body would still burn this many calories.
For most people, BMR accounts for 60-75% of total daily calorie expenditure. This means the majority of the calories you burn each day go toward basic biological functions, not exercise. This is why crash diets that go below your BMR are counterproductive — your body needs these calories to function properly.
How the Harris-Benedict equation works
Our calculator uses the original Harris-Benedict equation, one of the most widely used BMR formulas in nutrition science. It factors in your weight, height, age, and gender to estimate your resting metabolic rate. The formula was first published in 1919 and has been validated across numerous studies.
For men: BMR = 66.47 + (13.75 × weight in kg) + (5.003 × height in cm) - (6.755 × age). For women: BMR = 655.1 + (9.563 × weight in kg) + (1.850 × height in cm) - (4.676 × age). The gender difference exists because men typically carry more muscle mass, which burns more calories at rest.
BMR vs TDEE — why you need both
BMR tells you the absolute minimum calories your body needs. But you don't lie in bed all day — you walk, work, exercise, and even digesting food burns calories. Your Total Daily Energy Expenditure (TDEE) adds these activity calories on top of your BMR.
For weight loss, you should eat below your TDEE but above your BMR. This ensures a calorie deficit while giving your body enough fuel for basic functions. A deficit of 300-500 calories below your TDEE is generally safe and sustainable.
Ready for the next step? Use our TDEE Calculator to find your total daily calorie needs, or go straight to the Macro Calculator to split those calories into protein, carbs, and fat.