BMR Calculator
Use our free BMR calculator to calculate your basal metabolic rate based on your age, gender, height, and weight. This tool tells you how many calories your body needs each day just to maintain basic functions at rest, helping you plan your diet and fitness goals more effectively.
How to Use This BMR Calculator
Using this basal metabolic rate calculator is simple:
- Enter your age, gender, height, and weight.
- Select your preferred formula (Mifflin-St Jeor, Harris-Benedict, or Katch-McArdle)
- Click Calculate to see your BMR in calories per day.
- Use the activity multiplier table to find your total daily calorie needs.
What Is a BMR Calculator?
A BMR calculator is an online tool that estimates the number of calories your body burns while at complete rest. It uses your personal measurements to calculate your basal metabolic rate instantly, without any manual math.
People use a basal metabolic rate calculator to understand their daily calorie needs, set realistic weight loss or weight gain targets, and plan meals more accurately. Knowing your BMR is the first step toward managing your nutrition effectively.
This online BMR calculator supports multiple formulas and works for both men and women across all age groups.
What Is Basal Metabolic Rate?
Basal metabolic rate is the number of calories your body needs to maintain its basic functions while at complete rest. These functions include breathing, circulation, cell production, and maintaining body temperature.
BMR is measured in a fully rested, fasted state, typically after 12 hours without eating. At this point, the digestive system is inactive, and the body is using energy only to keep vital organs functioning.
For most people, BMR accounts for approximately 60-75% of total daily energy expenditure, depending on activity level and body composition. Physical activity makes up approximately 20%, and digestion accounts for the remaining 10%.
BMR Formulas
There are three widely used formulas to calculate BMR. Each uses a slightly different approach.
Mifflin-St Jeor Equation
The Mifflin-St Jeor equation is considered the most accurate formula for most people. It was introduced in 1990 and is the most commonly recommended formula for calculating BMR.
For men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
For women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
Revised Harris-Benedict Equation
The Harris-Benedict equation was one of the first BMR formulas developed. It was revised in 1984 to improve accuracy and was widely used until the Mifflin-St Jeor formula replaced it.
For men: BMR = (13.397 × weight in kg) + (4.799 × height in cm) − (5.677 × age) + 88.362
For women: BMR = (9.247 × weight in kg) + (3.098 × height in cm) − (4.330 × age) + 447.593
Katch-McArdle Formula
The Katch-McArdle formula calculates BMR based on lean body mass rather than total body weight. It is more accurate for people who know their body fat percentage, particularly those who are leaner or more muscular.
Formula: BMR = 370 + 21.6 × (1 − body fat %) × weight in kg
How to Calculate BMR
Example: A 30-year-old woman weighing 65 kg and 165 cm tall.
- Step 1: Use the Mifflin-St Jeor equation for women.
- Step 2: Apply the formula: BMR = (10 × 65) + (6.25 × 165) − (5 × 30) − 161
- Step 3: Calculate each part: 650 + 1031.25 − 150 − 161
- Step 4: BMR = 1,370.25 calories per day
This means her body burns approximately 1,370 calories per day at complete rest to maintain basic organ functions.
BMR and Daily Calorie Needs
BMR represents calories burned at rest only. To find your total daily calorie needs, multiply your BMR by an activity factor. This is known as your Total Daily Energy Expenditure (TDEE).
| Activity Level | Multiplier | Description |
|---|---|---|
| Sedentary | BMR × 1.2 | Little or no exercise |
| Lightly active | BMR × 1.375 | Exercise 1–3 times per week |
| Moderately active | BMR × 1.55 | Exercise 4–5 times per week |
| Very active | BMR × 1.725 | Intense exercise 6–7 times per week |
| Extra active | BMR × 1.9 | Very intense daily exercise or physical job |
Example: Using the BMR of 1,370 calories from the example above with a lightly active lifestyle:
TDEE = 1,370 × 1.375 = 1,883.75 calories per day
This is the total number of calories needed each day to maintain the current body weight at that activity level.
What Affects Your BMR?
Several factors influence your basal metabolic rate:
Age: BMR decreases with age. Older individuals generally require fewer calories at rest than younger people.
Gender: Men typically have a higher BMR than women because they tend to have greater muscle mass and a lower body fat percentage.
Muscle Mass: Muscle tissue requires more energy to maintain than fat tissue. People with more muscle mass have a higher BMR. Strength training can increase BMR over time by building muscle.
Body Size: Taller and heavier individuals generally have a higher BMR because their bodies require more energy to maintain a larger mass.
Genetics: Hereditary traits influence how efficiently the body uses energy, which can raise or lower BMR regardless of other factors.
Diet: Eating small, regular meals can slightly raise BMR. Severe calorie restriction or starvation can reduce BMR by as much as 30% as the body enters a conservation state.
Climate: Cold environments increase BMR because the body expends more energy to maintain a stable internal temperature.
BMR vs RMR
BMR and resting metabolic rate (RMR) are often used interchangeably, but they are not the same.
BMR is measured under strict conditions; the person must be fully rested, fasted for at least 12 hours, and in a temperature-controlled environment. RMR is measured under more relaxed conditions and is slightly higher than BMR because the body is in a resting but not fully inactive state.
For most practical purposes, such as diet planning and fitness goals, RMR and BMR are treated as equivalent values
FAQs
What is a BMR calculator?
A BMR calculator is an online tool that estimates the number of calories your body burns at rest each day based on your age, gender, height, and weight.
What does basal metabolic rate mean?
Basal metabolic rate is the number of calories your body needs to perform basic life-sustaining functions at complete rest, such as breathing, circulation, and maintaining body temperature.
Which BMR formula is most accurate?
The Mifflin-St Jeor equation is considered the most accurate for most people. The Katch-McArdle formula is more accurate for lean individuals who know their body fat percentage.
How do I calculate my BMR?
Enter your age, gender, height, and weight into the BMR calculator and click Calculate. The tool applies the selected formula and gives your result instantly.
What is the difference between BMR and TDEE?
BMR is the number of calories your body burns at rest. TDEE is your total daily calorie requirement, which includes physical activity. TDEE is calculated by multiplying BMR by an activity factor.
Does BMR change with age?
Yes. BMR decreases as you get older. This is one reason why weight management becomes more challenging with age, even if eating habits remain the same.
Can I increase my BMR?
Yes. Building muscle through strength training is the most effective way to raise BMR over time, since muscle tissue burns more calories at rest than fat tissue.
Is BMR the same as RMR?
They are similar but not identical. BMR is measured under stricter conditions, while RMR is measured in a relaxed state. RMR is slightly higher than BMR, but both are used for the same practical purposes.
How many calories should I eat based on my BMR?
Multiply your BMR by the activity multiplier that matches your lifestyle to find your TDEE. Eat at TDEE to maintain weight, below it to lose weight, and above it to gain weight.
Is this BMR calculator free?
Yes. Our online BMR calculator is completely free with no sign-up required.