BMI Calculator

Instantly calculate Body Mass Index (BMI)

Simply enter your height and weight to calculate your Body Mass Index (BMI) instantly. Provides obesity classification and health risk assessment based on WHO (World Health Organization) standards for free. Perfect tool for medical professionals, fitness trainers, and health-conscious individuals. All processing is done in your browser, ensuring complete privacy protection.

How to Use

Calculate BMI in 3 simple steps:

Enter Height

Enter your height in centimeters (cm) (e.g., 170cm)

Enter Weight

Enter your weight in kilograms (kg) (e.g., 65kg)

Instant Results

BMI value and obesity classification (WHO standards) are automatically displayed. You can also check the ideal weight range.

🔒 Privacy Protection: All calculations are performed in your browser. No entered data is sent to servers and is completely protected.

Results

Classification: --

Height (cm)

Weight (kg)

BMI Calculator

Height (cm)

Weight (kg)

WHO (World Health Organization) Classification Standards

WHO defines the following BMI standards:

• Below 16.00: Severe Thinness
• 16.00-17.00: Moderate Thinness
• 17.00-18.50: Mild Thinness
• 18.50-25.00: Normal
• 25.00-30.00: Overweight
• 30.00-35.00: Obese Class I
• 35.00-40.00: Obese Class II
• 40.00 and above: Obese Class III

BMI 25 or higher increases lifestyle disease risk, and BMI 30 or higher is classified as obese.

Obesity Classification	BMI Range	Health Risk
Severe Thinness (Severe Thinness)	< 16.00	Malnutrition, decreased immunity
Moderate Thinness (Moderate Thinness)	16.00 - 17.00	Malnutrition risk
Mild Thinness (Mild Thinness)	17.00 - 18.50	Underweight tendency
Normal (Normal)	18.50 - 25.00	Healthy
Overweight (Overweight)	25.00 - 30.00	Lifestyle disease risk ↑
Obese Class I (Obese Class I)	30.00 - 35.00	Lifestyle disease risk ↑↑
Obese Class II (Obese Class II)	35.00 - 40.00	Serious health risk
Obese Class III (Obese Class III)	≥ 40.00	Extremely serious health risk

Practical Use Cases

BMI calculator is widely used from health management to fitness and medical settings:

1. Health Checkups & Metabolic Syndrome Assessment

Used in corporate health checkups and comprehensive medical examinations to assess metabolic syndrome risk. BMI 25 or higher indicates obesity and helps evaluate lifestyle disease risks.

2. Diet & Weight Management

Can be used to assess current status before starting a diet or to track weight loss progress. Set ideal weight range as a goal to support healthy weight management.

3. Fitness & Training Planning

Used as an indicator when personal trainers evaluate client physique and create optimal training menus. Balance of aerobic and strength training is adjusted based on BMI value.

4. Medical Settings & Nutritional Guidance

Used as basic data when doctors and registered dietitians assess patient nutritional status and provide dietary therapy or nutritional guidance. Used to determine underweight (BMI<18.5) or obesity (BMI≥25).

5. Athletic Body Composition Management

Used as an indicator for athletes to maintain physique suitable for their sport. However, BMI tends to be high when muscle mass is high, so it should be evaluated in combination with body fat percentage.

6. Insurance & Health Risk Assessment

BMI is used as an important indicator in life insurance application screening and health risk assessment. Higher obesity increases lifestyle disease risk, serving as a reference for insurance premium calculation.

7. Childhood Growth Assessment

Pediatricians check children's growth curves and compare with age-specific BMI percentiles to assess development. Helps early detection of obesity or underweight.

What is BMI (Body Mass Index)?

BMI (Body Mass Index) is an international indicator of obesity calculated from height and weight.

BMI Calculation Formula

BMI = Weight(kg) ÷ Height(m) squared

Example: For height 170cm, weight 65kg
BMI = 65 ÷ (1.7 × 1.7) = 65 ÷ 2.89 = 22.5

This formula is universal worldwide, quantifying the balance between height and weight. BMI 22 is statistically considered the "ideal weight" with lowest disease risk.

BMI Limitations and Cautions

BMI is a convenient indicator but has the following limitations:

1. Does not consider muscle mass: Athletes and strength training enthusiasts have high muscle mass, leading to high BMI, but are not necessarily obese.

2. Does not reflect body fat percentage: BMI is calculated only from weight and height, so body fat percentage and visceral fat amount are unknown.

3. Differences by age, sex, and race: Elderly have reduced muscle mass, tending to lower BMI. Also, Asians tend to have higher lifestyle disease risk at lower BMI than Westerners.

4. Individual differences: Skeletal size and body type differences are not reflected.

Therefore, BMI should be used as a guide, and it's important to comprehensively assess health status in combination with body fat percentage, waist circumference, blood tests, etc.

Frequently Asked Questions

What is the normal BMI range?

According to WHO standards, BMI 18.5-25.0 is considered Normal. The Japan Society for the Study of Obesity defines BMI 22 as "ideal weight" as it's statistically associated with lowest disease risk. For example, for height 170cm, ideal weight is 1.7 × 1.7 × 22 = 63.6kg.

What's the problem with BMI 25 or higher?

BMI 25 or higher is classified as "Overweight" and increases risk of lifestyle diseases (diabetes, hypertension, dyslipidemia, etc.). BMI 30 or higher becomes "Obese" with further increased risk of heart disease, stroke, cancer, etc. Early weight management is recommended.

What happens if BMI is too low (below 18.5)?

BMI below 18.5 is classified as "Underweight" and increases risk of malnutrition, weakened immunity, osteoporosis, anemia, etc. Especially for women, there's also risk of menstrual irregularities and infertility. Proper nutrition and calorie intake are necessary.

Do muscular people have high BMI?

Yes, since muscle is heavier than fat, athletes and bodybuilders with high muscle mass tend to have high BMI. In this case, obesity cannot be determined by BMI alone. It's important to evaluate using body fat percentage and waist circumference together.

Can BMI be used for children?

For children, the same BMI standards as adults cannot be used. Since appropriate BMI differs by age and sex, "BMI percentile curves" are used. Pediatricians evaluate by comparing with growth curves. Generally, 85th percentile or higher is considered "obesity tendency".

What's the difference between BMI and body fat percentage?

BMI is an indicator of physique calculated from height and weight, while body fat percentage is the proportion of fat in body weight. BMI is convenient but doesn't distinguish between muscle and fat mass. Body fat percentage can be measured with a body composition analyzer; 15-20% for men and 20-25% for women is standard. Using both allows accurate health assessment.

How to calculate ideal weight?

Ideal weight is calculated as "Height(m) squared × 22". For example, for height 170cm, 1.7 × 1.7 × 22 = 63.6kg is ideal weight. BMI 22 is statistically associated with lowest disease risk. However, there's about ±10% range depending on individual skeletal structure and muscle mass.

How can I improve my BMI?

If BMI is high, gradually lose weight through balanced diet restriction and moderate exercise (aerobic and strength training). Aim for 3-5% body weight loss per month. If BMI is low, increase muscle mass through nutritious meals, increased calorie intake, and strength training. In either case, consulting a doctor or registered dietitian is recommended.