bmi calculator
Body Mass Index — metric & imperial — healthy weight range — no sign-up.
BMI is a screening tool, not a medical diagnosis. It does not account for muscle mass, bone density, age or ethnicity. Always consult a healthcare provider for a complete health assessment.
BMI categories — WHO standard
| Under 18.5 | Underweight |
| 18.5 – 24.9 | Normal weight |
| 25.0 – 29.9 | Overweight |
| 30.0 – 34.9 | Obese — Class 1 |
| 35.0 – 39.9 | Obese — Class 2 |
| 40.0 and over | Severely obese |
What is BMI?
Body Mass Index is calculated from your height and weight. Adopted by the WHO as a population screening tool — giving a rough indication of whether you carry a healthy amount of body weight for your height.
BMI formula
Metric: BMI = weight (kg) ÷ height (m)²
Imperial: BMI = (weight lbs ÷ height in²) × 703
FAQ
Is BMI accurate for athletes?
No — BMI does not distinguish muscle from fat. Athletes often show as overweight even when healthy. Waist circumference and body fat % are better indicators.
Is my data stored?
No — everything runs in your browser. Nothing is uploaded or saved.
What is a healthy BMI?
The WHO defines 18.5–24.9 as normal weight for most adults. For people over 65, a slightly higher BMI may be protective.
Does age affect BMI?
BMI uses the same formula for all adults, but older adults naturally carry more fat at the same BMI. The calculator notes your age for context only.