Calculate your Body Mass Index in seconds. See where you fall on the BMI scale, your healthy weight range, and what your number actually means for your health.
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Body Mass Index (BMI) is a simple ratio of your weight to your height squared. It was developed in the 1800s as a population-level statistical tool and is still widely used today because it requires no equipment and takes seconds to calculate.
BMI is a useful screening tool but it has real limitations. It doesn’t distinguish between muscle and fat — a muscular athlete and an unfit person can have the same BMI. It also doesn’t account for where you carry body fat, which matters significantly for health outcomes. Visceral fat (around your organs) carries more risk than subcutaneous fat (under the skin).
Use BMI as one data point alongside other measures — waist circumference, body fat percentage, and how you feel and perform physically are all meaningful signals that BMI misses.
The World Health Organization defines BMI ranges as follows: below 18.5 is underweight, 18.5 to 24.9 is normal weight, 25 to 29.9 is overweight, and 30 and above is obese. These thresholds are based on population-level data linking BMI to health outcomes across large studies.
Some researchers argue that the overweight threshold should be higher for people with more muscle mass or different body compositions, and that BMI classifications work less accurately for certain ethnic backgrounds. Asian populations, for example, may face elevated health risks at lower BMI thresholds.