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Body Mass Index is a quick snapshot of your weight relative to height. Enter your measurements below to find out where you stand.
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Understanding BMI
What is Body Mass Index?
Body Mass Index (BMI) is a numerical value calculated from a person's weight and height. It was developed by Belgian mathematician Adolphe Quetelet in the 19th century and has since become one of the most widely used screening tools in preventive medicine.
BMI does not directly measure body fat, but research has shown it correlates reasonably well with more precise measurements of body fat in most adults. It is used by doctors, dietitians, and researchers as a quick, cost-free initial screening for weight-related health risks.
| Category | BMI Range | Health Risk |
|---|---|---|
| Underweight | Below 18.5 | Malnutrition, bone loss risk |
| Normal weight | 18.5 – 24.9 | Lowest health risk |
| Overweight | 25.0 – 29.9 | Moderate increased risk |
| Obese Class I | 30.0 – 34.9 | High risk |
| Obese Class II+ | 35.0 and above | Very high risk |
The Formula
How BMI is Calculated
The BMI formula is straightforward and the same worldwide — only the units differ:
Metric: BMI = weight (kg) ÷ height² (m²)
Imperial: BMI = 703 × weight (lb) ÷ height² (in²)
For example, a person who weighs 70 kg and is 1.75 m tall has a BMI of 70 ÷ (1.75 × 1.75) = 22.9 — well within the healthy range.
Important Context
BMI Has Limitations
BMI is a useful starting point, but it is not a complete picture of health. It does not distinguish between fat mass and muscle mass, so a highly muscular athlete may register as "overweight" despite having low body fat.
Additionally, BMI does not account for fat distribution — where fat is stored on the body (especially around the abdomen) matters more than overall amount for many health risks. Age, sex, ethnicity, and bone density also influence what is "healthy" for a given individual.
What You Can Do
Maintaining a Healthy BMI
Sustainable habits beat short-term fixes. Here are evidence-backed pillars of long-term weight health:
Balanced Nutrition
Prioritise whole foods, adequate protein, and fibre. Avoid ultra-processed foods that are easy to overeat.
Regular Movement
At least 150 minutes of moderate activity weekly. Resistance training preserves muscle and boosts metabolism.
Quality Sleep
Poor sleep disrupts hunger hormones (ghrelin & leptin), increasing cravings and reducing willpower.
Hydration
Drinking water before meals can reduce caloric intake. Thirst is often mistaken for hunger.
Stress Management
Chronic stress raises cortisol, which promotes fat storage — especially around the abdomen.
Regular Check-ups
Annual health screenings catch trends early. Your doctor can pair BMI with blood work for a full picture.