Calculate Your BMI
Enter your height and weight to calculate your Body Mass Index and see your weight category.
BMI Results
Your BMI
Body Mass Index
0.0
kg/m²
Weight Category
WHO Classification
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Health Risk
Associated health risks
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Ideal Weight Range
Healthy BMI (18.5-24.9)
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BMI Categories
Underweight
Normal
Overweight
Obese
Weight Goal Calculator
Calculate how much weight you need to gain or lose to reach a healthy BMI.
Understanding BMI: A Complete Health Guide
Body Mass Index (BMI) is a simple calculation using a person's height and weight. The formula is BMI = kg/m² where kg is a person's weight in kilograms and m² is their height in meters squared. A BMI of 25.0 or more is overweight, while the healthy range is 18.5 to 24.9.
BMI Categories and Health Risks
The World Health Organization (WHO) defines these BMI categories:
Underweight: BMI less than 18.5
Increased risk of nutritional deficiencies, osteoporosis
Normal weight: BMI 18.5 to 24.9
Lowest health risk, maintain this range
Overweight: BMI 25 to 29.9
Increased risk of heart disease, diabetes
Obese Class I: BMI 30 to 34.9
High risk, consider weight loss program
Obese Class II: BMI 35 to 39.9
Very high risk, medical intervention needed
Obese Class III: BMI 40 or more
Extremely high risk, immediate medical care
Limitations of BMI
While useful for population studies, BMI has limitations:
- Muscle mass: Athletes may be misclassified as overweight due to high muscle mass
- Fat distribution: Doesn't account for where fat is stored (abdominal fat is more dangerous)
- Age and gender: May not be accurate for elderly, pregnant women, or certain ethnic groups
- Body composition: Doesn't measure body fat percentage or fitness level
- Health markers: Doesn't consider blood pressure, cholesterol, or blood sugar levels
Alternative Measurements
For a more complete health picture, consider these additional measurements:
- Waist circumference: Measure around your natural waist (above hip bones). Risk increases if > 102 cm (40 in) for men or > 88 cm (35 in) for women
- Waist-to-hip ratio: Divide waist circumference by hip circumference. Healthy is < 0.9 for men, < 0.85 for women
- Body fat percentage: More accurate but requires special equipment. Healthy ranges: Men 10-20%, Women 18-28%
Frequently Asked Questions
What is a healthy BMI range?
For adults, a healthy BMI is between 18.5 and 24.9. This range is associated with the lowest risk of health problems. For children and teens, BMI is interpreted differently using age and gender-specific percentiles.
How accurate is BMI?
BMI is a good screening tool but not diagnostic. It should be used alongside other measurements like waist circumference and body fat percentage. For most people, BMI provides a reasonable estimate of body fat, but it's less accurate for athletes, pregnant women, and the elderly.
Should BMI be different for men and women?
The same BMI categories apply to both men and women. However, women naturally have more body fat than men at the same BMI. For accuracy, consider gender-specific body fat measurements or waist circumference.
How often should I check my BMI?
For most adults, checking BMI every 3-6 months is sufficient unless you're actively trying to lose or gain weight. Rapid weight changes should be discussed with a healthcare provider.
BMI for Different Populations
BMI interpretation may vary for different groups:
- Children and teens: Use age and gender-specific BMI percentiles
- Older adults: May have higher health risks at lower BMIs
- Asian populations: May have higher health risks at lower BMIs (consider lower thresholds)
- Athletes: May have high BMI due to muscle mass, not fat
- Pregnant women: Use pre-pregnancy BMI to guide weight gain recommendations
Health Risks Associated with BMI
Underweight (BMI < 18.5)
Nutritional deficiencies, osteoporosis, weakened immune system
Normal (BMI 18.5-24.9)
Lowest risk of chronic diseases
Overweight (BMI 25-29.9)
Increased risk of type 2 diabetes, hypertension, heart disease
Obese (BMI ≥ 30)
High risk of multiple health problems including stroke, certain cancers, sleep apnea
Health Recommendations Based on BMI
If Your BMI is High
- Consult with a healthcare provider before starting any weight loss program
- Aim for 5-10% weight loss for significant health benefits
- Combine diet changes with regular physical activity
- Focus on sustainable lifestyle changes, not quick fixes
If Your BMI is Normal
- Maintain your current weight through balanced diet and regular exercise
- Continue monitoring your weight every 1-3 months
- Focus on overall health, not just weight
If Your BMI is Low
- Consult with a healthcare provider to rule out medical conditions
- Focus on nutrient-dense foods to gain weight healthily
- Consider strength training to build muscle mass
Important Note
This BMI calculator provides estimates for informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.