Even when you are asleep or lying perfectly still, your body is continuously consuming energy. Critical biological tasks, such as pumping blood through your heart, breathing, regulating body temperature, and synthesizing hormones, require a steady fuel supply. The amount of energy consumed under these resting conditions is known as your Basal Metabolic Rate (BMR).
Basal Metabolic Rate represents the absolute minimum number of calories your body needs to survive at complete rest. In most adults, BMR accounts for approximately 60% to 75% of their total daily energy expenditure.
Knowing your BMR is a valuable baseline. If you consume fewer calories than your BMR for long periods, your body may downregulate metabolic processes to preserve energy, a response commonly called starvation mode. Therefore, weight loss plans should target calorie intakes above BMR but below TDEE.
To plan your target daily calorie needs, try our daily calorie energy planner. To break down these baseline calories into macronutrient targets, check out our macronutrient ratios helper.
While historical formulas like the Harris-Benedict equation are still popular, modern clinical research indicates the Mifflin-St Jeor formula is the most accurate predictive standard:
- Male BMR:
BMR = 10 × Weight (kg) + 6.25 × Height (cm) - 5 × Age (years) + 5
- Female BMR:
BMR = 10 × Weight (kg) + 6.25 × Height (cm) - 5 × Age (years) - 161
To check if your weight fits healthy body standards, use our Body Mass Index classifier. For checking your body fat ratio, see our body fat percentage calculator.
Several physical factors determine your BMR: - Muscle Mass: Muscle tissue is metabolically active, burning more calories at rest than fat tissue. Increasing muscle increases BMR. - Age: BMR naturally declines as we age, primarily due to loss of muscle mass. - Genetics and Thyroid: Thyroid hormones regulate metabolic speed; imbalances can raise or lower BMR.
Additionally, environmental temperature and health status affect resting metabolic rate. In very cold climates, the body consumes extra energy to generate heat and maintain core body temperature, which temporarily spikes BMR. Similarly, running a fever during an illness increases metabolic rate as the immune system works harder.
To check average weight targets for your height, see our ideal weight solver. For converting height or weight units, use our standard measurement conversions tool. For verifying standard arithmetic math, try our everyday daily math helper.
Suppose a 30-year-old female weighs 65 kg, and is 165 cm tall.
First, calculate the weight and height contributions: - Weight factor: 10 × 65 = 650. - Height factor: 6.25 × 165 = 1,031.25.
Next, calculate the age contribution: - Age factor: 5 × 30 = 150.
Plug into the female Mifflin-St Jeor formula: - BMR = 650 + 1,031.25 - 150 - 161 - BMR = 1,531.25 - 150 - 161 ≈ 1,370 calories/day.
This means her body burns approximately 1,370 calories per day before adding any movement or exercise. To analyze ratio targets across diets, try our relative ratio solver.