BMI Calculator
Calculate Body Mass Index (BMI) in metric (kg/cm) or imperial (lbs/in). Instantly shows your BMI value and weight category — underweight, normal, overweight, or obese.
Your BMI
22.5
Healthy weight
How to use the bmi calculator
Pick metric or imperial, enter your height and weight, and the BMI updates instantly along with the WHO category. BMI is a screening tool — it doesn't account for muscle mass, age, or body composition.
Formula & explanation
Metric: BMI = weight (kg) ÷ height (m)². Imperial: BMI = (weight (lbs) ÷ height (in)²) × 703. WHO categories: < 18.5 underweight, 18.5–24.9 healthy, 25–29.9 overweight, ≥ 30 obese.
Examples
A 170 cm person weighing 65 kg has a BMI of 22.5 (healthy). A 5'7" person at 145 lbs is BMI 22.7.
Frequently asked questions
- What is a healthy BMI range?
- The WHO defines: below 18.5 = underweight, 18.5–24.9 = healthy weight, 25–29.9 = overweight, 30 or above = obese. These thresholds apply to most adults but have limitations.
- Is BMI accurate for athletes?
- Not very. Muscular people often score 'overweight' despite low body fat, because BMI doesn't distinguish muscle from fat. Use it as a screening tool, not a definitive assessment.
- What about children?
- Children use age- and sex-specific BMI percentiles, not the adult cutoffs above. The same raw BMI value has a different meaning at different ages. Consult a pediatrician.
- Does BMI differ by ethnicity?
- Yes. Some health organizations recommend lower overweight thresholds for South Asian, East Asian, and other populations due to differences in body composition at equivalent BMI values.
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