BMI Calculator
Calculate your Body Mass Index (BMI) by entering your weight and height. See your BMI category and healthy weight range.
What is BMI?
Body Mass Index (BMI) is a simple measurement that uses your height and weight to estimate whether you are underweight, normal weight, overweight, or obese. It is widely used by healthcare professionals as a screening tool.
BMI Formula
For imperial units:
BMI Categories (WHO Standard)
- Underweight: BMI less than 18.5
- Normal weight: BMI 18.5 to 24.9
- Overweight: BMI 25.0 to 29.9
- Obese (Class I): BMI 30.0 to 34.9
- Obese (Class II): BMI 35.0 to 39.9
- Obese (Class III): BMI 40.0 or more
Limitations of BMI
BMI does not directly measure body fat. Athletes with high muscle mass may have a high BMI without being overweight. BMI also does not account for age, sex, ethnicity, or body composition. It should be used as a general indicator, not a definitive diagnosis.
BMI Calculation Example
For a person weighing 70 kg with a height of 170 cm (1.7 m):
- BMI = 70 / (1.7 × 1.7) = 70 / 2.89 = 24.2
- Category: Normal weight
For the same height, a healthy weight range would be approximately 53.5 kg to 72.0 kg.
Frequently Asked Questions
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A healthy BMI range is between 18.5 and 24.9 according to the World Health Organization (WHO). This range is associated with the lowest risk of weight-related health issues.
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BMI may not be accurate for athletes or people with high muscle mass, as muscle weighs more than fat. A muscular person may have a high BMI but a healthy body fat percentage. Other measurements like body fat percentage or waist-to-hip ratio may be more appropriate.
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Standard adult BMI categories apply to both men and women aged 20 and above. For children and teens (ages 2-19), BMI is interpreted using age- and sex-specific percentiles. Older adults may have slightly different healthy ranges.
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For imperial units, the formula is: BMI = (weight in pounds / (height in inches)2) × 703. For example, a person weighing 154 lbs at 67 inches tall has a BMI of (154 / 4489) × 703 = 24.1.
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BMI is a useful screening tool but not a diagnostic one. Higher BMI is generally associated with increased risk of heart disease, type 2 diabetes, and other conditions. However, factors like diet, physical activity, and genetics also play important roles.
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Checking your BMI once every few months is sufficient for most adults. If you are on a weight management plan, your doctor may recommend more frequent checks along with other health metrics.