BMR Calculator
BMR Calculator
The Basal Metabolic Rate (BMR) Calculator estimates the amount of energy your body expends while at rest in a neutral environment and in a post-absorptive state (after approximately 12 hours of fasting). This measurement reflects the energy required to maintain vital bodily functions such as heart rate, breathing, and brain activity.
To use the calculator, adjust the values below and click “Calculate.” You can switch between US Units, Metric Units, and Other Units.
Input Fields:
- Age:
Example: 25 years (range: 15–80) - Gender:
Select male or female - Height:
Example: 180 cm - Weight:
Example: 60 kg - + Settings:
Customize additional parameters, such as activity level and equation type.
Result:
BMR = 1,605 Calories/day
Save this calculation for future reference.
Daily Calorie Needs Based on Activity Level:
| Activity Level | Calories |
|---|---|
| Sedentary: little or no exercise | 1,926 |
| Exercise 1–3 times/week | 2,207 |
| Exercise 4–5 times/week | 2,351 |
| Daily exercise or intense exercise 3–4 times/week | 2,488 |
| Intense exercise 6–7 times/week | 2,769 |
| Very intense exercise daily or physical job | 3,050 |
Definitions:
- Exercise: 15–30 minutes of elevated heart rate activity.
- Intense Exercise: 45–120 minutes of elevated heart rate activity.
- Very Intense Exercise: 2+ hours of elevated heart rate activity.
Understanding BMR
Basal Metabolic Rate (BMR) is the energy your body needs to maintain essential functions while at rest. Think of it as the fuel an idle car consumes when parked. Approximately 70% of your daily energy expenditure goes toward maintaining vital organs like the heart, brain, kidneys, and lungs. Physical activity accounts for about 20%, while digestion (thermogenesis) uses the remaining 10%.
BMR is measured under strict conditions: awake, rested, and in a fasting state. It is the largest component of your total daily caloric needs, which can be estimated by multiplying your BMR by an activity factor (ranging from 1.2 for sedentary lifestyles to 1.9 for highly active individuals).
BMR Equations
The calculator uses three primary equations to estimate BMR. You can select your preferred formula in the settings:
- Mifflin-St Jeor Equation (Most Accurate):
- For Men: BMR = 10W + 6.25H – 5A + 5
- For Women: BMR = 10W + 6.25H – 5A – 161
- Revised Harris-Benedict Equation:
- 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 (Accounts for Lean Body Mass):
- BMR = 370 + 21.6(1 – F)W Where:
- W = Weight (kg)
- H = Height (cm)
- A = Age (years)
- F = Body Fat Percentage
Factors Influencing BMR
- Muscle Mass:
- Anaerobic exercises like weightlifting increase muscle mass, raising BMR.
- Aerobic exercises (e.g., running) have no direct effect on BMR.
- Age:
- BMR decreases with age due to reduced muscle mass and metabolic activity.
- Genetics:
- Hereditary factors can influence metabolic rate.
- Weather:
- Cold environments increase BMR as the body works to maintain temperature.
- Extreme heat can also raise BMR as the body expends energy to cool down.
- Diet:
- Frequent, small meals can boost BMR.
- Starvation or severe calorie restriction can lower BMR by up to 30%.
- Pregnancy:
- BMR increases to support fetal development.
- Supplements:
- Certain supplements, like caffeine, can temporarily raise BMR.
BMR vs. RMR
While often used interchangeably, BMR and Resting Metabolic Rate (RMR) differ slightly:
- BMR is measured under strict, fully rested conditions.
- RMR is measured in a relaxed state and may vary based on context.
Accuracy of BMR Calculations
Even the most precise BMR calculations are estimates. A 2005 meta-analysis* revealed that 26% of metabolic rate variation remains unexplained, highlighting the complexity of human physiology. While BMR provides a useful baseline for estimating daily caloric needs, tracking your diet, exercise, and progress over time is the best way to achieve health and fitness goals.
Related Tools:
- Body Fat Calculator
- Calorie Calculator
Reference:
Johnstone AM, Morison SD, Duncan JS, et al. Factors influencing variation in basal metabolic rate include fat-free mass, fat mass, age, and circulating thyroxine but not sex, circulating leptin, or triiodothyronine. Am J CLIN Nutra. 2005;82(5):941-948.