Body Mass Index (BMI) is the most widely used screening tool for assessing whether a person is underweight, normal weight, overweight, or obese. While BMI has limitations, it remains the standard starting point for health assessment used by doctors worldwide. Our free BMI Calculator computes your BMI instantly, shows your health category, and gives you the ideal weight range for your height.
What Is BMI?
BMI is calculated by dividing your weight in kilograms by the square of your height in metres: BMI = weight (kg) / height (m)^2. For example, a person who weighs 70 kg and is 1.75 m tall has a BMI of 70 / (1.75 x 1.75) = 22.9. Our calculator handles both metric (kg and cm) and imperial (lbs, feet, and inches) inputs automatically.
BMI Categories
- Below 18.5 — Underweight. May indicate malnutrition, an eating disorder, or other health conditions.
- 18.5 to 24.9 — Normal weight. Associated with the lowest risk of weight-related health problems.
- 25.0 to 29.9 — Overweight. Increased risk of cardiovascular disease, type 2 diabetes, and hypertension.
- 30.0 to 34.9 — Obese Class I. High health risk requiring medical attention.
- 35.0 to 39.9 — Obese Class II. Very high health risk.
- 40.0 and above — Obese Class III. Extremely high health risk, also called morbid obesity.
BMI Limitations
BMI is a useful screening tool but has known limitations. It does not directly measure body fat percentage — a muscular athlete may have a high BMI despite very low body fat. It does not account for age-related muscle loss in older adults. BMI thresholds may also need adjustment for Asian populations, where health risks increase at lower BMI values (typically above 23 for overweight). Always consult a healthcare professional for a comprehensive health assessment.
Your Ideal Weight Range
Our calculator also shows your ideal weight range — the weight range corresponding to a BMI between 18.5 and 24.9 for your specific height. This gives you a concrete target if you are working on weight management. The range is calculated directly from the BMI formula reversed for your height, so it is specific to you rather than a generic chart.
Calculate Your BMI Now
Open the free BMI Calculator, enter your weight and height in metric or imperial units, and get your BMI, health category, and ideal weight range instantly. No login, no data collection.
