BMI Calculator
Check your Body Mass Index instantly — free, metric & imperial, no signup needed
< 18.5
18.5 – 24.9
25 – 29.9
≥ 30
About this BMI calculator
Our BMI calculator computes your Body Mass Index from your height and weight. BMI is a quick screening measure used worldwide to identify possible weight-related health risks in adults.
Key features
- Dual units: Supports both metric (kg, cm) and imperial (lbs, ft/in)
- WHO standards: Uses World Health Organization BMI classifications
- Instant results: Calculates in your browser — nothing is sent to a server
- Clear interpretation: Explains what your BMI means in plain language
Understanding your BMI — what the number really means
Your Body Mass Index is a simple ratio of your weight to your height. It gives a quick indication of whether your weight is in a healthy range for your height. While it is not a direct measure of body fat, it is a widely used and practical screening tool recommended by health organisations across the world.
Why BMI can sometimes be misleading
Muscle mass
Athletes and muscular people often show a high BMI even when their body fat is low, because muscle is denser than fat.
Gender differences
Women naturally carry more body fat than men at the same BMI. The same number can mean different things depending on sex.
Age variations
Older adults may lose muscle over time, giving a normal BMI while their body fat percentage is actually higher than ideal.
When BMI is most useful
Health risk screening: A high BMI is associated with increased risk of type 2 diabetes, high blood pressure, and heart disease. Knowing your BMI is the first step to addressing these risks.
Tracking changes over time: Even if the absolute number is imperfect, tracking your BMI over weeks and months tells you whether your weight is moving in the right direction.
For Indians and Asians: Research shows that South Asians carry health risks at lower BMI values. A BMI of 23 or above is considered overweight for Indians, compared to 25 for the global WHO standard.
Free, instant, no signup required.
Frequently asked questions
What is BMI and why is it useful?
BMI (Body Mass Index) measures body fat relative to height and weight. It is a widely recommended screening tool that helps identify possible weight-related health issues quickly and without specialist equipment.
How is BMI calculated?
BMI = weight (kg) divided by height (m) squared. For imperial units: [weight (lbs) / height² (inches)] × 703. Our calculator handles the unit conversion automatically — just enter your measurements and click Calculate.
What are the WHO BMI categories?
Underweight: below 18.5. Normal weight: 18.5–24.9. Overweight: 25–29.9. Obese: 30 and above (further split into Class I: 30–34.9, Class II: 35–39.9, Class III: 40 and above).
Is BMI accurate for everyone?
Not always. BMI can overestimate risk in muscular individuals and underestimate it in older adults who have lost muscle. Athletes, pregnant women, and children require different assessments. Always consult a doctor for a full evaluation.
What is a healthy BMI for Indians?
For South Asians, a BMI of 23 or above is considered overweight and 27.5 or above is considered obese — lower thresholds than the global WHO standard (25 and 30), because Asians carry higher health risk at lower BMI values.