BMR Calculator
Estimate the energy expended at rest in a temperate, post-absorptive state (requiring about 12 hours of fasting).
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ages 15-80
What is BMR?
Basal Metabolic Rate (BMR) is the energy expended at rest in a temperate, post-absorptive state (requiring about 12 hours of fasting). Think of it as the energy needed to keep your body running while at complete rest - like an idle car that's still consuming fuel to keep the engine running.
Energy is used to maintain vital organs including the heart, brain, kidneys, nervous system, intestines, liver, lungs, sex organs, muscles, and skin. Approximately 70% of daily calories are used for basic upkeep, 20% for physical activity, and 10% for food digestion (thermogenesis).
BMR Estimation Equations
Mifflin-St Jeor Equation (1990)
Generally considered the most accurate for most people.
For men: BMR = 10W + 6.25H - 5A + 5
For women: BMR = 10W + 6.25H - 5A - 161
Revised Harris-Benedict Equation (1984)
One of the earliest equations, revised in 1984.
For men: BMR = 13.397W + 4.799H - 5.677A + 88.362
For women: BMR = 9.247W + 3.098H - 4.330A + 447.593
Katch-McArdle Formula
Calculates Resting Daily Energy Expenditure (RDEE) and accounts for lean body mass.
BMR = 370 + 21.6(1 - F)W
Where:
- W = body weight in kg
- H = body height in cm
- A = age
- F = body fat in percentage
BMR Variables
Muscle Mass
Anaerobic exercises (like weight-lifting) increase BMR by building muscle mass, which increases resting energy consumption.
Age
Older age generally leads to a lower BMR or lower minimum caloric intake for organ maintenance.
Genetics
Hereditary traits influence BMR and can account for up to 20% of the variance in BMR.
Weather
Cold environments raise BMR due to the energy required for homeostatic regulation.