Last updated: 3 October 2026
Reviewed by Jordan Morley, FA Level 2 Football Coach
Basal Metabolic Rate is the energy your body needs for basic functions — breathing, circulation, cell production — while completely at rest. It accounts for the majority of most people's daily calorie burn. The Mifflin-St Jeor equation is the most accurate common way to estimate it from your age, sex, height and weight. Multiplying BMR by an activity factor gives your total daily energy expenditure (TDEE).
- Calories burned at complete rest
- Largest part of daily energy use
- Estimated via Mifflin-St Jeor equation
- BMR × activity factor = TDEE
In practice
BMR represents the calories your body burns just staying alive — organ function, breathing, cell repair — before any movement is factored in, and it typically makes up 60-75% of total daily energy expenditure for most people, which is why it's the starting point for any calorie or macro calculation rather than an afterthought.
FAQ
How is BMR different from TDEE?
BMR is calories burned at complete rest with zero activity; TDEE adds on top of BMR the calories burned through daily movement, exercise and digestion, giving your true total daily energy need.
Does muscle mass affect BMR?
Yes — muscle tissue burns more calories at rest than fat tissue, so individuals with more lean mass generally have a higher BMR even at the same bodyweight.