Summary of multipliers used to calculate Total Daily Energy Expenditure (TDEE) from Basal Metabolic Rate (BMR).
Activity Level	Multiplier (TDEE Factor)	Description
Sedentary	1.2	Little to no exercise, desk job.
Lightly Active	1.375	Light exercise or sports 1-3 days/week.
Moderately Active	1.55	Moderate exercise or sports 3-5 days/week.
Very Active	1.725	Hard exercise or sports 6-7 days/week.
Extra Active	1.9	Very hard exercise or sports, physical job, or training twice a day.

Understanding Your Basal Metabolic Rate (BMR)

What is Basal Metabolic Rate (BMR)?

Basal Metabolic Rate, or BMR, represents the minimum number of calories your body needs to perform essential life-sustaining functions while at rest. These functions include breathing, circulating blood, maintaining body temperature, cell production, and brain and nerve function. Essentially, it's the energy your body burns just to keep you alive and functioning if you were to do absolutely nothing – not even digest food. Understanding your BMR is a fundamental step in managing your weight and optimizing your nutritional intake.

This calculator helps you estimate your BMR using scientifically recognized formulas and then uses that to estimate your Total Daily Energy Expenditure (TDEE), which accounts for your activity level. Knowing your BMR is crucial for anyone looking to lose weight, gain weight, or simply maintain a healthy body composition. It provides a baseline for your body's energy needs, allowing for more informed dietary and exercise decisions.

BMR Formula and Explanation

The most widely accepted and accurate formula for calculating BMR is the Mifflin-St Jeor Equation. It takes into account your biological sex, weight, height, and age.

The Mifflin-St Jeor Equation:

For Men: BMR = (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) + 5
For Women: BMR = (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) – 161

Explanation of Variables:

Variables and their units used in BMR and TDEE calculations.
Variable	Meaning	Unit	Typical Range
Weight	Your body weight	Kilograms (kg) or Pounds (lbs)	(e.g., 45-200+ kg)
Height	Your body height	Centimeters (cm), Inches (in), or Feet & Inches	(e.g., 140-200+ cm)
Age	Your age in completed years	Years	(e.g., 18-80+)
Gender	Biological sex (influences the constant offset in the formula)	Male / Female	N/A
BMR	Basal Metabolic Rate	Kilocalories per day (kcal/day)	(e.g., 1200-2500 kcal/day)
Activity Level Factor	Multiplier representing daily physical activity	Unitless	1.2 – 1.9
TDEE	Total Daily Energy Expenditure	Kilocalories per day (kcal/day)	(BMR * Activity Level Factor)

Total Daily Energy Expenditure (TDEE)

While BMR tells you how many calories you burn at rest, TDEE estimates your total daily calorie burn, including all activities. It's calculated by multiplying your BMR by an Activity Level Factor. This factor accounts for the calories burned through daily movement, exercise, and the thermic effect of food (TEF).

TDEE = BMR × Activity Level Factor

Practical Examples

Let's see how the calculator works with two different individuals:

Example 1: Sarah, a Moderately Active Woman

Inputs:
Biological Sex: Female
Weight: 65 kg
Height: 165 cm
Age: 30 years
Activity Level: Moderately active (1.55)

Calculation:

BMR = (10 × 65) + (6.25 × 165) – (5 × 30) – 161

BMR = 650 + 1031.25 – 150 – 161 = 1370.25 kcal/day

TDEE = 1370.25 × 1.55 = 2123.89 kcal/day

Results: Sarah's estimated BMR is approximately 1370 kcal/day, and her TDEE is about 2124 kcal/day. To maintain her weight, she needs to consume around 2124 calories daily.

Example 2: Michael, a Sedentary Man

Inputs:
Biological Sex: Male
Weight: 80 kg
Height: 180 cm
Age: 45 years
Activity Level: Sedentary (1.2)

Calculation:

BMR = (10 × 80) + (6.25 × 180) – (5 × 45) + 5

BMR = 800 + 1125 – 225 + 5 = 1705 kcal/day

TDEE = 1705 × 1.2 = 2046 kcal/day

Results: Michael's estimated BMR is approximately 1705 kcal/day, and his TDEE is about 2046 kcal/day. Since he's sedentary, his TDEE is only slightly higher than his BMR.

How to Use This Online BMR Calculator

Select Biological Sex: Choose 'Male' or 'Female' as the formula constants differ.
Enter Weight: Input your current weight and select the appropriate unit (kg or lbs).
Enter Height: Input your height and select the correct unit (cm, in, or ft'in"). The calculator will convert units internally.
Enter Age: Provide your age in years.
Choose Activity Level: Select the option that best describes your typical daily physical activity. This is crucial for estimating your TDEE.
Calculate: Click the "Calculate BMR & TDEE" button.
Review Results: The calculator will display your estimated BMR (calories burned at rest) and TDEE (total daily calories burned). It will also show target calorie ranges for losing or gaining approximately 1 lb per week.
Interpret: Use your TDEE as a guide for your daily caloric intake. To lose weight, consume fewer calories than your TDEE; to gain weight, consume more.
Copy or Reset: Use the "Copy Results" button to save your findings or "Reset" to start over with new inputs.

Key Factors That Affect BMR

Body Composition (Muscle vs. Fat): Muscle tissue is metabolically more active than fat tissue. Individuals with higher muscle mass have a higher BMR. Strength training can help increase muscle mass and thus BMR over time.
Age: BMR generally decreases with age, starting to decline significantly after age 20-30. This is partly due to a natural loss of muscle mass.
Biological Sex: Men typically have a higher BMR than women due to having more muscle mass on average and a higher body water content.
Genetics: Your inherited genes play a role in your metabolic rate. Some people naturally have a faster metabolism.
Hormonal Factors: Thyroid hormones, in particular, significantly regulate metabolism. Conditions like hypothyroidism (underactive thyroid) lower BMR, while hyperthyroidism (overactive thyroid) raises it.
Body Size and Surface Area: Larger bodies require more energy to maintain. BMR is often correlated with body surface area.
Diet: Severe calorie restriction or prolonged dieting can lower your BMR as your body adapts to conserve energy.
Environmental Temperature: Extreme cold or heat can increase BMR as the body works harder to maintain its core temperature.

FAQ about BMR Calculation

Q1: How accurate is the Mifflin-St Jeor equation?
A1: The Mifflin-St Jeor equation is considered one of the most accurate BMR prediction formulas currently available for the general adult population. However, it is still an estimate, and individual metabolic rates can vary.
Q2: Can I use pounds and inches directly in the calculator?
A2: Yes, this online BMR calculator allows you to select your preferred units (kg/lbs for weight, cm/in for height). The tool automatically converts them to kilograms and centimeters internally, as required by the Mifflin-St Jeor formula.
Q3: What is the difference between BMR and TDEE?
A3: BMR is the calories your body burns at complete rest. TDEE (Total Daily Energy Expenditure) includes the calories burned from BMR plus all physical activities throughout the day. TDEE is a more realistic measure of your daily calorie needs.
Q4: My BMR seems low. Why might this be?
A4: Several factors can contribute to a lower BMR, including being older, having a lower muscle mass percentage, being female, or having certain hormonal conditions. If you have concerns, consult a healthcare professional.
Q5: How much should I reduce my calories to lose weight?
A5: A common guideline is a deficit of 500 calories per day to lose about 1 pound (0.45 kg) per week. However, it's important not to drop below your BMR or a dangerously low calorie intake (consult a doctor or dietitian).
Q6: Does this calculator account for pregnancy or breastfeeding?
A6: No, this standard BMR calculator is not designed for pregnant or breastfeeding individuals, as their caloric needs are significantly higher and require specialized calculations often provided by healthcare professionals.
Q7: How does muscle mass affect BMR?
A7: Muscle tissue burns more calories at rest than fat tissue. Therefore, individuals with a higher percentage of muscle mass will generally have a higher BMR. Strength training can help increase muscle mass and potentially boost BMR.
Q8: What if my height is in feet and inches?
A8: When selecting "Feet & Inches" for height, you would typically enter the total height. For example, 5'10" could be entered as 70 inches. Some more advanced calculators might ask for feet and inches separately, but for simplicity here, ensure your input corresponds correctly to the total measurement (e.g., enter 70 for 5'10" if it's interpreted as total inches, or adjust your entry based on how the input field expects it).

Online Basal Metabolic Rate Calculator

Online Basal Metabolic Rate (BMR) Calculator

Your Results

TDEE vs. BMR Breakdown

Activity Level Factors