The calories your body burns at complete rest.
Enter your age, sex, weight and height to see your Basal Metabolic Rate from the Mifflin-St Jeor equation, cross-checked against Harris-Benedict, plus your estimated daily burn at five activity levels.
Your details
Your current age in years.
Biological sex affects metabolic rate.
Your weight in pounds.
Feet portion of your height.
Inches portion of your height.
The headline number uses the Mifflin-St Jeor equation, the most accurate predictive BMR formula for most adults. Results update as you type.
What your BMR means
Your daily burn at each activity level
Calorie targets built on your BMR
TDEE at all five activity levels
Each row multiplies your Mifflin-St Jeor BMR by the standard activity factor. The highlighted row is the sedentary baseline used in the result card.
| Activity level | Factor | TDEE (kcal/day) | Typical week |
|---|
BMR, explained
What is Basal Metabolic Rate?
Basal Metabolic Rate (BMR) is the number of calories your body needs to perform basic life-sustaining functions at complete rest. These functions include breathing, circulation, cell production, nutrient processing, and temperature regulation. BMR typically accounts for 60-75% of your total daily calorie expenditure.
Mifflin-St Jeor vs Harris-Benedict
The Mifflin-St Jeor equation (1990) is considered the most accurate for most people, using the formula: Men: 10 × weight(kg) + 6.25 × height(cm) - 5 × age - 161; Women: same but subtract 161 instead of adding 5. The Harris-Benedict equation (1919, revised 1984) is older but still widely used and may be slightly more accurate for very active or obese individuals.
Factors That Affect BMR
Several factors influence BMR beyond age, sex, and body size. Muscle mass is the biggest controllable factor, more muscle means higher BMR. Genetics play a role in natural metabolic rate. Hormones, particularly thyroid hormones, significantly impact metabolism. Environmental temperature, certain medications, and even caffeine can temporarily alter BMR.
Using BMR for Fitness Goals
Knowing your BMR is the foundation for any diet or fitness plan. Multiply your BMR by an activity factor (1.2 for sedentary to 1.9 for very active) to estimate Total Daily Energy Expenditure. From there, create a calorie surplus or deficit based on whether you want to gain muscle or lose fat. Never eat fewer calories than your BMR for extended periods.
Common questions
What is the most accurate BMR formula?
The Mifflin-St Jeor equation is considered the most accurate predictive equation for BMR in most adults, according to the American Dietetic Association. It was developed in 1990 using modern data and tends to be within 10% of measured values.
How can I increase my BMR?
The most effective way to increase BMR is building lean muscle mass through resistance training, as muscle tissue burns more calories at rest than fat tissue. Eating adequate protein, staying hydrated, and getting enough sleep also support a healthy metabolic rate.
Is BMR the same as resting metabolic rate?
BMR and Resting Metabolic Rate (RMR) are similar but not identical. BMR is measured under strict conditions (complete rest, fasted state, thermoneutral environment). RMR is measured under less restrictive conditions and is typically 10-20% higher than BMR.
Why does BMR decrease with age?
BMR decreases with age primarily because of the natural loss of muscle mass (sarcopenia), which begins around age 30. Hormonal changes, including declining growth hormone and testosterone levels, also contribute. Regular resistance training can significantly slow this decline.
BMR equations are population-level estimates, not laboratory measurements, and individual metabolic rates commonly vary by 10 percent or more from any formula. This tool is for information only and is not medical or dietary advice. Do not start a restrictive diet, eat below your estimated BMR for extended periods, or make treatment decisions based on these numbers alone: talk to a doctor or registered dietitian first, especially if you have a thyroid condition, diabetes, an eating disorder history or any chronic illness.