BMI Calculator

What is BMI (Body Mass Index)?

Body Mass Index (BMI) is a simple, widely-used screening measure calculated from a person's weight and height. Healthcare professionals use it to quickly classify whether an individual is underweight, normal weight, overweight, or obese — and to flag potential weight-related health risks early. It does not directly measure body fat, but it correlates with direct fat measures and is a useful population-level screening tool.

BMI Formula

Metric: BMI = weight (kg) ÷ height² (m²)
Imperial: BMI = [weight (lbs) ÷ height² (inches²)] × 703

BMI Categories — WHO Standard Classification

BMI Range	Category	Health Risk Level
Below 18.5	Underweight	Risk of malnutrition, bone loss, immune issues
18.5 – 24.9	Normal weight	Lowest risk — maintain healthy habits
25.0 – 29.9	Overweight	Moderate risk of heart disease, Type 2 diabetes
30.0 – 34.9	Obese Class I	High risk — lifestyle changes strongly advised
35.0 – 39.9	Obese Class II	Very high risk
40.0 and above	Obese Class III	Severe risk — immediate medical attention advised

BMI for Indians — Why the Cut-offs Are Different

Research shows that South Asians, including Indians, develop metabolic conditions like Type 2 diabetes and cardiovascular disease at lower BMI levels compared to Western populations. Several Indian health organisations and the WHO Expert Consultation recommend using BMI ≥ 23 as overweight and BMI ≥ 27.5 as obese for Asian adults. Our calculator uses the global WHO classification — keep this context in mind when interpreting your result.

BMI Limitations

BMI does not distinguish between muscle mass and fat mass. Athletes, bodybuilders, and physically active individuals often show a high BMI despite having very low body fat. Conversely, older adults may have a "normal" BMI but carry excess fat with low muscle mass (sarcopenic obesity). For a complete picture, use BMI alongside waist circumference, body fat percentage, and clinical assessment by a doctor.

Frequently Asked Questions

How do I calculate my BMI?

Divide your weight in kilograms by your height in metres squared: BMI = kg ÷ m². Use the calculator above for an instant result — enter weight, height, age, and gender.

What is a healthy BMI for adults in India?

The globally accepted normal BMI range is 18.5–24.9. For Indians specifically, a BMI of 23–24.9 may already indicate increased metabolic risk — consult a doctor if your BMI is above 23 and you have other risk factors.

Is a BMI of 20 healthy?

Yes — a BMI of 20 is in the Normal Weight range (18.5–24.9) and is considered healthy for most adults.

Can BMI be inaccurate?

Yes, in certain cases. Athletes with high muscle mass may have a high BMI but low body fat. Pregnant women, elderly individuals, and children require different assessment methods. BMI is best used as one of several indicators rather than a standalone measure.

What should I do if my BMI is high?

A high BMI is a signal — not a diagnosis. Start with a calorie deficit plan, check your BMR and TDEE, and consult a registered dietitian or doctor for a personalised plan. Small, sustainable changes in diet and activity can significantly improve BMI over time.