Calculate Your BMI
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Underweight
<18.5Normal
18.5–24.9Overweight
25–29.9Obese
30+
<18.5Normal
18.5–24.9Overweight
25–29.9Obese
30+
Your BMI
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Healthy Range
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Weight to Ideal
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What Is BMI (Body Mass Index)?
BMI is a simple numerical measurement that uses your height and weight to estimate whether you're at a healthy weight. Developed by Belgian mathematician Adolphe Quetelet in the 1830s, it's now the most widely used screening tool for weight-related health risks worldwide.
BMI Formula
BMI = Weight (kg) ÷ Height (m)²
In Imperial units: BMI = (Weight in lbs × 703) ÷ Height in inches²
Example Calculation
Weight: 70 kg, Height: 175 cm (1.75 m)
BMI = 70 ÷ (1.75 × 1.75) = 70 ÷ 3.0625 = 22.9 (Normal weight)
BMI Categories
| BMI Range | Category | Health Risk |
|---|---|---|
| < 16.0 | Severe Underweight | High (malnutrition, immune issues) |
| 16.0 – 16.9 | Moderate Underweight | Moderate |
| 17.0 – 18.4 | Mild Underweight | Low-Moderate |
| 18.5 – 24.9 | Normal Weight | Low (optimal) |
| 25.0 – 29.9 | Overweight | Moderate (increased risk) |
| 30.0 – 34.9 | Obese Class I | High |
| 35.0 – 39.9 | Obese Class II | Very High |
| ≥ 40.0 | Obese Class III (Morbid) | Extremely High |
Asian BMI Standards
The WHO recommends different thresholds for Asian populations due to higher body fat percentage at the same BMI:
- Underweight: < 18.5
- Normal: 18.5 – 22.9
- Overweight: 23.0 – 24.9
- Obese: ≥ 25.0
Limitations of BMI
While BMI is a useful screening tool, it has important limitations:
- Doesn't distinguish fat from muscle: Athletes and bodybuilders may be classified as "overweight" despite having low body fat.
- Ignores fat distribution: Belly fat (visceral fat) is more dangerous than fat on hips/thighs. BMI doesn't measure where fat is stored.
- Age and gender blind: Older adults naturally have more body fat. Women typically have more fat than men at the same BMI.
- Doesn't account for bone density: People with denser bones may appear heavier without excess fat.
- Not suitable for children: Children's BMI should be compared to age-and-sex-specific percentile charts.
Better Complementary Measures
- Waist-to-hip ratio: < 0.85 for women, < 0.90 for men is healthy
- Waist circumference: < 80 cm (women), < 90 cm (men) for Asian populations
- Body fat percentage: 10–20% for men, 18–28% for women is typically healthy
Health Risks by BMI Category
| Condition | Underweight | Normal | Overweight | Obese |
|---|---|---|---|---|
| Heart Disease | — | Low | Increased | High |
| Type 2 Diabetes | — | Low | Moderate | High |
| Hypertension | — | Low | Moderate | High |
| Sleep Apnea | — | Low | Moderate | Very High |
| Joint Problems | — | Low | Moderate | High |
| Osteoporosis | High | Low | Very Low | Very Low |
| Immune Function | Weakened | Normal | Normal | Weakened |
Related Calculators
Frequently Asked Questions
A BMI between 18.5 and 24.9 is considered healthy for most adults. For Asian populations, the healthy range is 18.5 to 22.9 due to different body composition. BMI should be used alongside other measures like waist circumference for a complete picture.
BMI is a useful screening tool but not a diagnostic one. It doesn't distinguish between muscle and fat mass, so very muscular or athletic people may have high BMI despite being healthy. It's best used alongside waist circumference and body fat percentage measurements.
The standard BMI categories are the same for adult men and women of all ages. However, older adults and women tend to have higher body fat at the same BMI. For children, BMI is interpreted using age-and-sex-specific growth charts (percentiles).
Most insurance companies consider BMI 18.5–30 as standard risk. BMI above 30 may attract higher premiums or extra medical tests. Some insurers in India use 18.5–27 as the preferred range. Check with your specific insurer for their criteria.
No. All calculations happen locally in your browser. Your height and weight data is never sent to any server, stored, or transmitted. Your health information stays completely private on your device.