Understanding This Calculator
Body Mass Index (BMI) is a screening measure that relates body weight to height. It’s the metric the World Health Organization (WHO) and CDC use to classify weight status at a population level, and it remains the fastest way to get a rough read on whether your weight falls in a typical range for your height.
BMI does not distinguish between muscle and fat mass, so athletes and very muscular individuals can register as ‘overweight’ despite low body fat. Use BMI alongside waist circumference or body-fat percentage for a fuller picture.
- kg body weight in kilograms
- m² height in meters, squared
| BMI Range | Category | General Guidance |
|---|---|---|
| Below 18.5 | Underweight | May indicate insufficient energy intake |
| 18.5 – 24.9 | Normal weight | Associated with lowest health risk |
| 25.0 – 29.9 | Overweight | Increased risk of related conditions |
| 30.0+ | Obese | Consult a healthcare provider for guidance |
Frequently Asked Questions
Is BMI accurate for everyone?
No. BMI doesn’t account for muscle mass, bone density, or fat distribution, so it can misclassify athletes, older adults, and certain ethnic groups. It’s a screening tool, not a diagnosis.
What’s a healthy BMI target?
18.5–24.9 is the WHO ‘normal weight’ band associated with the lowest average health risk, though individual context (muscle mass, frame size, health history) matters.