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BMI Calculator FREE

Calculate your BMI (Body Mass Index) online free. Supports metric and imperial units. See weight category and healthy weight range. No sign-up.

BMI Score
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BMI Calculator

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Frequently Asked Questions

BMI (Body Mass Index) is a simple numerical value calculated from a person's height and weight, used as a screening tool to identify potential weight-related health risks. The formula is: BMI = weight in kg / (height in metres)^2. For imperial units, the formula is: BMI = (weight in pounds x 703) / (height in inches)^2. A BMI of 18.5 to 24.9 is classified as normal weight by the World Health Organisation.
BMI does not distinguish between fat mass and muscle mass. A professional athlete with high muscle density may have a high BMI while having a healthy body fat percentage. Conversely, an elderly person with low muscle mass (sarcopenia) may have a normal BMI while having a high body fat percentage. BMI is also less accurate for children, pregnant women, very short individuals, and some ethnic populations who have different healthy weight ranges than the standard WHO tables.
The standard BMI calculation and categories are the same for both sexes, but interpretation may differ. At the same BMI, women typically have a higher percentage of body fat than men. Some health professionals use sex-specific assessment tools like body fat percentage measurements, waist-to-hip ratio, and waist circumference for more personalised assessment. The WHO's global BMI categories are widely used as a population-level screening tool despite these individual-level limitations.
According to the World Health Organisation, a BMI between 18.5 and 24.9 is classified as normal weight. Below 18.5 is underweight. 25.0 to 29.9 is overweight. 30.0 and above is classified as obese, subdivided into Class I (30-34.9), Class II (35-39.9), and Class III (40 and above, sometimes called morbid obesity). Some Asian populations have higher metabolic risk at lower BMI values, and several Asian countries use a lower threshold of 23 for overweight.
Yes. All calculations run entirely in your browser using JavaScript arithmetic. No height, weight, age, or health data is ever sent to any server, stored in any database, or accessible to anyone other than you on your own device. Closing your browser tab permanently removes all entered data.

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Free BMI Calculator Online — Calculate Body Mass Index with Metric and Imperial Units

Body Mass Index is one of the most widely used health screening tools globally, recommended by the World Health Organisation, the NHS, the CDC, and most national health authorities as a simple first-pass indicator of weight-related health risk. The BMI Calculator on OneDocPDF calculates BMI in both metric (kilograms and centimetres) and imperial (pounds, feet, and inches) units, displays the WHO weight category, shows the healthy weight range for your height, and provides a visual indicator on the BMI scale — all running locally in your browser with zero data transmission.

While BMI is a useful population-level screening tool, it has well-documented limitations at the individual level. Athletes, bodybuilders, and people with high muscle mass may be classified as overweight or obese despite excellent metabolic health. Older adults with muscle loss (sarcopenia) may have a normal BMI despite an elevated body fat percentage. For these reasons, healthcare professionals increasingly use BMI alongside other assessments such as waist circumference, waist-to-hip ratio, body fat percentage measured by DEXA or bioelectrical impedance, and blood lipid panels for comprehensive metabolic health evaluation.

For other health-related calculations, see our Age Calculator for precise age calculations. For financial health planning tools, see our EMI Calculator and Percentage Calculator. All tools on OneDocPDF are completely free and private.