BMI & NIH Body Composition Calculator
Professional Health Assessment Tool
Calculate your Body Mass Index (BMI), body fat percentage, waist-to-hip ratio, and comprehensive health risk assessment with professional accuracy for men and women.
Body Mass Index (BMI) Calculator
✓ Easy to Use
Enter your height and weight to calculate your BMI. BMI is a measure of body fat based on height and weight that applies to adult men and women.
Select your gender for accurate assessment
Age affects body composition
Weight in pounds
Your BMI
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kg/m²
Body Mass Index
BMI Category
–
Classification
–
Healthy Weight Range
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Pounds / Kilograms
For your height
Weight to Reach Goal
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Pounds / Kilograms
–
BMI Progress
⚠️ Important Information
BMI is a screening tool and may not accurately reflect body fat for athletes, elderly individuals, or those with high muscle mass. It’s best used alongside other health assessments. Always consult with a healthcare provider for personalized health advice.
Body Fat Percentage Calculator
✓ Advanced Analysis
Calculate your body fat percentage using the U.S. Navy Method, which includes waist, neck, and hip measurements for more accurate body composition analysis.
Gender affects body fat calculation
Age is used in calculations
Height in inches
Weight in pounds
Measure below larynx
Measure at navel for men, smallest width for women
Measure at largest horizontal measure
Body Fat Percentage
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%
U.S. Navy Method
Body Fat Category
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Classification
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Fat Mass
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lbs
Total body fat weight
Lean Mass
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lbs
Muscle and bone weight
Body Fat Category Reference
| Category | Women (%) | Men (%) | Description |
|---|---|---|---|
| Essential Fat | 10-13% | 2-5% | Minimum fat needed for health |
| Athletes | 14-20% | 6-13% | Fit, athletic individuals |
| Fitness | 21-24% | 14-17% | Good fitness level |
| Average | 25-31% | 18-24% | Average body fat |
| Obese | 32%+ | 25%+ | Elevated health risk |
⚠️ Measurement Tips
For accurate results: Measure neck below the larynx with tape sloping downward. Measure waist at navel level (men) or smallest width (women). Measure hips at the largest horizontal measure. Take measurements while standing relaxed, not flexing muscles.
Waist-to-Hip & Waist-to-Height Ratio
✓ Health Risk Assessment
Waist circumference and waist-to-hip ratio are strong indicators of abdominal fat and health risk. These measurements help assess risk for heart disease, diabetes, and other conditions.
Gender affects risk thresholds
Height in inches
Measure at navel level
Measure at largest point
Waist-to-Hip Ratio
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Ratio
Lower is better
Waist-to-Height Ratio
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Ratio
Should be < 0.5
Health Risk Level
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Assessment
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Waist Circumference Risk
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Classification
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Health Risk Reference
| Measurement | Low Risk | Moderate Risk | High Risk |
|---|---|---|---|
| Waist (Men) | < 37 in | 37-40 in | > 40 in |
| Waist (Women) | < 31.5 in | 31.5-34.6 in | > 34.6 in |
| WHR (Men) | < 0.95 | 0.95-1.0 | > 1.0 |
| WHR (Women) | < 0.80 | 0.80-0.85 | > 0.85 |
⚠️ Important Note
Waist circumference is a strong predictor of health risk related to excess abdominal fat. Even with a normal BMI, a large waist circumference may indicate increased health risk. Consult your healthcare provider for personalized health assessment.
Understanding BMI and Body Composition
📚 Educational Resources
Learn about BMI, body fat percentage, waist measurements, and how to use these tools for health assessment.
What is BMI?
Body Mass Index (BMI) is a measure of body fat based on height and weight that applies to adult men and women. It is calculated by dividing weight in kilograms by height in meters squared (kg/m²).
BMI Categories (WHO/CDC):
- Underweight: BMI less than 18.5
- Normal weight: BMI 18.5 – 24.9
- Overweight: BMI 25.0 – 29.9
- Obese: BMI 30.0 and above
BMI Limitations:
- May overestimate body fat in muscular individuals
- May underestimate body fat in older adults or those with low muscle mass
- Doesn’t account for bone density or body composition
- May underestimate risk for people of Asian descent
Understanding Body Fat Percentage
Body fat percentage is the proportion of your total body weight that is fat. It’s a more accurate measure of body composition than BMI alone, as it distinguishes between fat mass and lean mass (muscle, bone, organs).
Why Body Fat Matters:
- Essential fat is necessary for hormone production and organ protection
- Excess body fat, especially visceral fat, increases disease risk
- Body fat percentage is more accurate than BMI for athletes
- Helps track progress during fitness and weight loss programs
Healthy Body Fat Ranges:
- Women: 18-25% (fitness), 25-31% (average)
- Men: 10-17% (fitness), 18-24% (average)
- Varies by age, genetics, and fitness level
Waist Circumference & Health Risk
Waist circumference is a strong indicator of abdominal (visceral) fat, which is more closely associated with health risks than overall body fat. Even with a normal BMI, excess abdominal fat increases risk for heart disease, diabetes, and other conditions.
Health Risk Thresholds:
- Men: High risk if waist > 40 inches (102 cm)
- Women: High risk if waist > 35 inches (88 cm)
- Waist-to-hip ratio > 1.0 (men) or > 0.85 (women) indicates increased risk
- Waist-to-height ratio should ideally be < 0.5
How to Measure:
- Waist: Measure at navel level, with tape snug but not tight
- Hip: Measure at the widest point of your hips
- Take measurements while standing relaxed
- Measure twice for accuracy
Health Recommendations
Regular Exercise
Aim for 150 minutes of moderate activity per week
Healthy Diet
Focus on whole foods, vegetables, and lean proteins
Quality Sleep
Aim for 7-9 hours of sleep per night
Stay Hydrated
Drink plenty of water throughout the day
Stress Management
Practice meditation, yoga, or other relaxation techniques
Regular Checkups
Visit your healthcare provider for regular health assessments
⚠️ Medical Disclaimer
This calculator is for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult with a qualified healthcare provider regarding your health and weight management. Results may vary based on individual factors such as muscle mass, bone density, and body composition.