BMI Calculator
Body Mass Index with healthy range
BMI is a simple number calculated from your height and weight. It gives a quick indication of whether your weight is in a healthy range — though it has real limitations worth knowing about.
Understanding BMI and Its Limitations
Weight Categories
The World Health Organization defines four main categories: below 18.5 is underweight, 18.5–24.9 is healthy, 25–29.9 is overweight, and 30 or above is obese. These ranges apply to most adults.
Different Thresholds for Asian Populations
Research shows that people of Asian descent face higher health risks at lower BMI values. Many Asian health guidelines treat a BMI over 23 as overweight and over 25 as obese — lower than the standard WHO thresholds.
Why BMI Isn't Perfect
BMI only looks at your height and weight — it can't tell the difference between muscle and fat. Athletes and very muscular people often score in the "overweight" range even when they're in excellent health. Use it as a starting point, not a final answer.
BMI = weight(kg) / height(m)² BMI Classification — WHO Standard
| Category | BMI range | Health risk |
|---|---|---|
| Underweight | < 18.5 | Nutritional deficiency risk |
| Normal weight | 18.5 – 24.9 | Lowest health risk |
| Overweight | 25.0 – 29.9 | Increased risk |
| Obese class I | 30.0 – 34.9 | High risk |
| Obese class II | 35.0 – 39.9 | Very high risk |
| Obese class III | ≥ 40.0 | Extremely high risk |
Frequently Asked Questions
What is a healthy BMI?
A BMI between 18.5 and 24.9 is considered healthy by the World Health Organization. Below 18.5 is underweight, and 25 or above is overweight.
Why can BMI be misleading for athletes?
BMI doesn't distinguish between muscle and fat. Someone with a lot of muscle mass may have a high BMI even if their body fat is low. For athletes, other measures like body fat percentage are more useful.
Are BMI ranges different for Asian people?
Yes. Many Asian health guidelines use lower thresholds — a BMI over 23 is considered overweight, and over 25 is obese — because health risks tend to appear at lower BMI values in Asian populations.
Can I use BMI as a medical diagnosis?
No. BMI is a screening tool only. It can flag potential concerns, but a proper health assessment from a doctor is needed for any diagnosis.
What happens if I enter the wrong units?
The result will be wrong. Make sure you select the right unit system (metric or imperial) before entering your measurements. You can switch using the toggle at the top of the calculator.
What formula does this BMI calculator use?
Metric: BMI = weight (kg) ÷ height (m)². Imperial: BMI = 703 × weight (lb) ÷ height (in)². Both give the same result when units are correctly entered.