BMI Calculator
Calculate Body Mass Index
Health Disclaimer
BMI calculations are for general informational purposes only and should not be used as a substitute for professional medical advice. BMI may not accurately reflect health status for athletes, elderly, pregnant women, or individuals with certain medical conditions. Always consult healthcare professionals for personalized health assessments and medical advice. TopCalculatorOnline is not responsible for any health decisions made based on these calculations.How This BMI Calculator Works
Our free BMI Calculator instantly determines your Body Mass Index using your height and weight. It supports both metric (kg/cm) and imperial (lbs/ft-in) units and shows your BMI category, healthy weight range, and how much weight you would need to gain or lose to reach a normal BMI.
BMI is a widely-used screening tool recommended by the World Health Organization (WHO) and the National Institutes of Health (NIH) to classify adults as underweight, normal weight, overweight, or obese. While BMI does not directly measure body fat, it correlates with more direct measures and is a useful starting point for assessing weight-related health risks.
BMI Formula Explained
BMI is calculated differently depending on your unit system:
Metric: BMI = weight (kg) / height (m)2
Imperial: BMI = (weight (lbs) × 703) / height (inches)2
For example, a person who weighs 70 kg and is 175 cm (1.75 m) tall would have a BMI of 70 / (1.75 × 1.75) = 22.9, which falls in the "Normal weight" category.
BMI Categories
| BMI Range | Category | Health Risk |
|---|---|---|
| Below 18.5 | Underweight | Malnutrition risk, osteoporosis, weakened immune system |
| 18.5 - 24.9 | Normal weight | Lowest risk of weight-related health issues |
| 25.0 - 29.9 | Overweight | Increased risk of heart disease, diabetes, high blood pressure |
| 30.0 - 34.9 | Obese Class I | High risk of cardiovascular disease and type 2 diabetes |
| 35.0 - 39.9 | Obese Class II | Very high risk of health complications |
| 40.0+ | Obese Class III | Extremely high risk, may require medical intervention |
BMI Limitations
- Athletes and muscular people: BMI may classify muscular individuals as overweight because it cannot distinguish between muscle and fat.
- Elderly: Older adults may have a higher BMI due to decreased muscle mass and increased fat, even at a "normal" weight.
- Children and teens: BMI-for-age percentiles (not standard BMI) should be used for people under 20.
- Pregnancy: BMI is not applicable during pregnancy due to expected weight gain.
- Ethnic variations: Some populations may have different health risk thresholds for the same BMI value.
Frequently Asked Questions
Related health tools: BMR Calculator to find your daily calorie needs, Body Fat Calculator for a more detailed body composition analysis, or Pregnancy & Ovulation Calculator.
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