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    BMI Calculator

    Calculate your BMI with this free online BMI calculator in kg/cm or lb/ft-in. See your WHO or Asian BMI category and the healthy weight range for your height.

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    About the BMI Calculator

    A BMI calculator works out your body mass index from your height and weight, in metric (cm and kg) or US units (feet, inches and pounds). It shows your BMI, the weight category it falls into, the healthy weight range for your height and how much you would need to gain or lose to reach it.

    BMI is weight in kilograms divided by height in metres squared; in US units it is 703 × weight in pounds ÷ height in inches squared. For adults the World Health Organization uses these categories: under 18.5 is underweight, 18.5 to 24.9 is a healthy weight, 25 to 29.9 is overweight and 30 or more is obesity. Many Asian populations face higher health risks at a lower BMI, so you can switch to the lower Asian cut-offs. The same formula and categories apply to men and women.

    BMI is a quick screening number, not a diagnosis. It does not distinguish muscle from fat, so very muscular people can score as overweight, and it is not suitable for children and teenagers, who need age- and sex-specific percentiles. Talk to a doctor about what your number means for you.

    When to use it

    • Checking whether your weight is in the healthy range for your height
    • Setting a realistic target weight for a diet or fitness plan
    • Tracking changes in BMI over months of weight loss or gain
    • Quick screening before a health check-up or insurance form

    Worked examples

    175 cm and 70 kg

    70 ÷ 1.75² = 22.9, a healthy BMI. The healthy weight range for this height is about 56.7 to 76.3 kg.

    US units: 5 ft 9 in and 160 lb

    703 × 160 ÷ 69² = 23.6, also in the healthy range.

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    How to use BMI Calculator

    1. 1Choose Metric (cm, kg) or US units (ft, in, lb)
    2. 2Enter your height and weight, then click Calculate BMI
    3. 3Read your BMI, weight category, healthy weight range and how much to gain or lose; switch to Asian cut-offs if they apply to you

    Frequently asked questions

    How is BMI calculated?▾

    BMI = weight in kilograms ÷ (height in meters)². In US units it equals 703 × weight in pounds ÷ (height in inches)². For example, 70 kg at 1.75 m gives 70 ÷ 3.0625 = 22.9.

    What is a healthy BMI?▾

    For adults the WHO healthy range is 18.5 to 24.9. 25 to 29.9 is overweight and 30 or more is obesity (class I 30–34.9, class II 35–39.9, class III 40+).

    Is BMI different for men and women?▾

    No. Adult BMI uses the same formula and the same categories for men and women, although women typically carry more body fat at the same BMI.

    Why are there Asian BMI cut-offs?▾

    The WHO found that many Asian populations have higher health risks at lower BMI, so it suggested overweight from 23 and obesity from 27.5. Singapore, India, Hong Kong and others use these cut-offs.

    What is BMI Prime?▾

    BMI Prime is your BMI divided by 25, the upper limit of normal. A value of 0.74–1.00 is in the healthy range; 1.20 means you are 20% above the upper limit.

    Does this BMI calculator work for children?▾

    No. For children and teens (2–19), BMI must be compared to age- and sex-specific growth percentiles. This calculator uses adult categories.

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