BMR Calculator (UK)
Calculate the calories your body burns at rest using the Harris–Benedict equation. Plan a deficit or surplus from your true baseline.
Basal Metabolic Rate (BMR) Explained
Basal Metabolic Rate (BMR) is the minimum number of calories your body requires to perform basic life-sustaining functions at rest. This includes breathing, circulating blood, cellular production, nutrient processing, and temperature regulation.
BMR accounts for approximately 60% to 75% of your total daily calorie burn. It is calculated using formulas like the Harris-Benedict equation or the Mifflin-St Jeor equation, which factor in age, biological sex, weight, and height. Because muscle tissue requires more energy than fat tissue at rest, increasing your lean muscle mass will elevate your BMR over time.
Knowing your BMR helps you determine your metabolic baseline. You should never consume fewer calories than your BMR for extended periods unless under strict medical supervision, as doing so can trigger metabolic slowdown, nutrient deficiencies, and muscle loss.
Frequently Asked Questions
Q: What is BMR?
BMR stands for Basal Metabolic Rate, representing the energy your body expends just to stay alive at rest, without any activity or food digestion factored in.
Q: Does eating below BMR damage metabolism?
Consuming calories below your BMR for too long can cause adaptive thermogenesis (metabolic slowdown) where your body conserves energy and burns muscle for fuel.